@Spiritspiral7  
Yes, I agree Sunset was less power hundry, and had a friendship (at least of sorts, even if Sunset didn’t admit it) with Flash. I mean, In Rainbow Rocks Sunset stated she knew what she done was wrong, and regretted it, just pushed those thoughts and feelings back. Or her words - Deep down, I guess I knew I was making a big mistake, and I wanted to still have a way to reach out to her.
 
Also, it’s from a Sunset x Sci-Twi series, but you might like this pic, as something like this possibly happened:  
>>1499262p (deleted)
 
An interesting that Sunset also was similar to Celestia in her look during her first Fall Formall:  

 
I don’t think it’s an accident - and I think Sunset (possibly subconciously) modeled herself on Celestia then. Which further implies she was more moral then.
 
And when Sunset loses all of her memories in A Friendship to Remember, and will in Forgotten Friendship, Sunset is confused and scared.
 
I think though Sunset was obsessed kinda with power, but somewhat like Sci-Twi, largelly out of fascination. But I guess overtime, Sunset grew more bitter and hatefull towards Celestia. I mean, most of her plan in the first movie, can be seen as her taking revenge on Celestia. Or alternatelly it was (subconciously) at least a way for Sunset to try to get Celestia’s attention, as A Friendship to Remember gives some fuell to the idea Sunset views Celestia as a mother figure.

@BackgroundLoL  
I agree that it is mostly speculation, I kinda stated that at the beginning. See I’m a pretty casual viewer. That’s I have haven’t really much evidence to back my opinion. I can just give you my view on all the evidence you present me.
 
As for my speculation about Sunset maybe lying or being mistaken. That picture of her from the previous Fall Formal shows she was not always a terrible person, but after the first movie she made the claim that she was always as bad as she was when they first met her. Also(again speculation, but one that does make sense) Sunset seems to enjoy playing the guitar(and she may have picked that up from Flash). So that could be genuinely good memory for the two of them. And the fact that they dated at all. Flash definitely wouldn’t have started dating her if she was a jerk at the time. She could have maybe faked it, but as I said earlier she really isn’t that convincing. And Flash clearly isn’t easily fooled as the false picture scene from the first movie would prove(and yes that scene was VERY poorly done, but I think the point can still stand). So I believe their relationship(romantic or platonic) must have started before she become obsessed with fame and power. He very well may have been her very first friend and she just did realize it.

@Spiritspiral7  
Oh, okay. Sorry I misunderstood you.
 
Well that’s speculation, and if we follow Occam’s razor, ie that one should assume without other evidence, the simplest answer is the most probable to be true, and the simplest one, is that Sunset stated the truth.
 
Maybe it’s me, but I don’t really see evidence that would indicate otherwise, for reasons I listed bellow.
 
With the memories, I meant that Sunset is willing, among things, to errase all of her memories of the reall world (which includes all memories of Flash), to save the humane 6’s friendship. Dunno, this just makes it come of to me the girls are more important to Sunset than Flash, at least of now.
 
(And what I meant before, that if they were a couple, or growing into one, I think she would at least somewhat reminiscence about her romance of Flash, or memories of him she will lose, seeing Sunset then gave up all of her memories of the human (including all memories of Flash, and of her theoretical love or crush on him, past or current). So I think she would then at least mention him, especialy that Flash, in the book at least, or was at least, like 10-20 feet away. Dunno, alternatelly one explain it maybe just Sunset cares that much about Friendship, than romance…)
 
[EDIT]  
Again, the above is just my subjective opinion.  
[END EDIT]
 
 
But still, I just want to sum up, that both that if Sunset has or had romantic feelings to Sci-Twi (or even even pony Twilight), or Flash, is rather an area of speculation, at least as now.

@BackgroundLoL  
I’m not saying it comes out of nowhere. I’m just saying personally it would feel very weird.
 
And just as a thought, there could be a number of reasons she would lie to her friends(or even herself) about her past relationship with Flash. I tend to think they had a closer connection than she lets on(or maybe even realized before her redemption)
 
And yes as you said she never even mentioned Flash with the whole memories thing and the mane 6 are closer to her. Makes sense because they basically saved her life and taught her friendship. And wasn’t involved in any of that. So it makes sense he wouldn’t come to mind.

@Spiritspiral7  
I write in the comment bellow “Well, it isn’t really/exactly shown as platonic,”, but I meant since start to write “Well, it isn’t really/exactly shown as non-platonic/romantic,”.

@Spiritspiral7
 
Well, it isn’t really/exactly shown as platonic, but I think Sunset with both Twilights, especially Sci-Twi, has tons of chemistry.
 
And well, one could state the same about Flash and Sunset, that Sunset sees Flash like a brother - as I mentioned, Sunset stated she never liked him romantically in Rainbow Rocks , and they had just three reall interractions, two reall conversations, those being them just exchanging advice, or Sunset being nice to Flash (and messed up his hair, which is more sibling-like, than romantic). (And in A Friendship to Remember/Forgotten Friendship, Sunset exchanged among things ALL of her memories of Flash, to save the Humane Six’s frendship, at least strongly implying the Humane 6 is closer to her..)
 
I mean, if anything Sunset had more romantically looking chemistry with Sci-Twi, than with Flash:  
 
 
 
 
 
>>1577134t (merged)  

 
While it may come mostly from Sunset, we have also stuff from Sci-Twi - she described Sunset as Dayream Shimer as beautiful - this may not seem much, but is one of the only (if not the only, but I’m not sure) examples a person/pony so in both FiM and Equestria Girls - and this a moment later after Spike told only really Sunset could talk Twilight out of leaving the camp, ie only Sunset could keep here there. Not Timber.
 
So I think the creators if they want to have Sci-Twi and Sunset as a couple, they left some clues till now.
 
Sorry, but if you say Sunset x Sci-Twi becoming canon would come of as forced/unexpected, the same, arguably more so, could be said about Flash x Sunset becoming canon (again 3 solid interractions, two reall conversations on screen…).
 
To be clear, I don’t mean to be rude o forcecull on my views, but to me, stating Sci-Twi and Sunset becoming a couple (ir rather, being developed into one) would come out of nowere, isn’t true…

@BackgroundLoL  
Honestly I’m hoping it’s portrayed as nothing more than platonic. As I mentioned before, I’ve always thought of Twilight and Sunset as sisters. If it turns into romantic shipping, it’s just not gonna feel right to me. And it’s not because they’re both girls(just in case anyone thinks I’m homophobic).

@Spiritspiral7  
Also, it’s now fully confirmed “A Friendship to Remember”, will become a hour long special - “Forgotten Friendship”:  
https://www.equestriadaily.com/2018/01/new-1-hour-equestria-girls-special.html
 
So the book is canon…

@ChuymaruZ  
You mean “A Friendship to Rember”, or my comment about the possible hints that the creators also kinda ship Sci-Twi with Sunset?

@BackgroundLoL  

@Spiritspiral7  
Well, I didn’t mean romantically close when formulating my argument, just indeed platonically. But I do think Sunset is closer to Twilights, than to Flash - I mean, she had three shown interractions with Flash, and many more with both Twilights, and has multiple statements about their closeness, in multiple works, including novels, whenever fully canon, or not. I mean, there is a reason why wroters so emphasize Sunset’s closedness to both Twilights.
 
An example is that Sunset made a facebooks statement (official by Hasbro) about someone/somepony, it was about both Twilights.:  
My friend Twilight Sparkle was there for me, and now it’s my turn to be there for her. — Sunset Shimmer
 
But I think we agree Sunset is at least probably closer to both Twilights, than to Flash, if (more probably) in a sisterly kind of love.
 
About that picture, yes from it I also think Sunset was most probably less villainous at the start, and became a villain overtime, especially that in Rainbow Rocks she told she knew deep down in her heart, she shouldn’t do what she done, and felt bad about it, just denied those feelings.
 
About “A Friendship to Remember”, it’s a very well writen book about Sunset, and many want it to be canon, for stuff like Sunset returning for a bit longer to Equestria, Sunset finally interracting again with Celestia, nd they making up, and Sunset and pony Twilight meeting again, as well as pony Twilight again having a role in Equestria Girls.  
The books also gives quite a bit evidence to the theory Celestia is a mother-figure to Sunset
 
Basically, many want the book to be made into an episode (which it may be), as it would tie Equestria Girls more to FiM, and show Sunset is canon to the (ridiculous by this point) deniers.
 
Also, about Sunset’s meltdown, she may had very meant BOTH Twilight being the most important people to her, as the memories of them, and feelings about them are tied, and Sunset was undergoing a despair even horison, and had her memories disapearing, hence the conflation.
 
Also, the scenes in the trailer to the new Equestria Girls specials, seem to show events from the book , as noted in comments by well known fandom figure,  
Gian Song yim - We’re getting an animated version of A Friendship to Remember”. <3 That beach scene looks ripped straight from the book. Can’t wait for Sunset/Celestia reunion
 
About Sunset being paired romantically with Twilight, particulary Sci-Twi, I think even the creators kinda ship them, just cannot make it canon (at least now) because of non straight relatonships being still controversial in cartoons.
 
I mean, they included (or rather will include) this scene:  

 
This is a pose (friends pushing a two people to embrace or kiss), that is used fairly exclusivelly to depict a romantic relationship. Other examples:  
 

 

 
I don’t think the similarity is an accident.
 
There is other stuff, like the lyrics there is other stuff, like lyrics in the Legend You Are Meant To Be, in a fragment describing how Sunset helped Twilight, having at least arguably some subtext  
Take my hand, I’m here for you  
Come away with me  
“Come away with me” sounds at least a bit romantic.
 
Some noted the part of the song, resembles, and might be referncing the definitevelly romantic well known song by Elvis Presley - Can’t Help Falling In Love - Take my hand / take my whole life too / for I can’t help / falling in love with you
 
Another background message, this time more literal, is that Sunset and Sci-Twi are paired in the background, in the form of mop puppets, as if holding hands:  

 
About Sunset though not stopping Twilight from being with Timber, and recoiling it with her loving Sci-Twi romantically, it can be explained by I Want my Beloved to be Happy , as depiced for example in this comic:  

 
Again, those are just my interpretations/theories, but the “hints” from creators do look interesting, and the ones I mentioned, are not even all such…

@BackgroundLoL  
I’m not gonna say anything about the novel stuff(if you want me to, then I’ll send another reply) because as I said: things from other sources are only “possible” canon to me. Neither confirmed or denied. That’s just me.
 
Sunset writing to Twilight, being very happy to see her, and being upset when she’s not there makes me think of Twilight’s relationship with Celestia. A teacher and student relationship.
 
Sunset protectiveness makes me think of her and Twilight as siblings. Which they were both Celestia’s students and she kinda acts like a mother to her students, so that kind of re-enforce that sibling vibe for me.
 
When Sunset “ditched” Flash, Flash didn’t have any major issues going on at that time(unlike Twilight). If he did she probably would have been a little more considerate and maybe assured him that they would talk later. Also after her suspicions about were gone, she encouraged Twilight to pursue Timber as a boyfriend and didn’t seem concerned about losing Twilight. So I don’t think she has those kinds of feelings for her. Also when Flash mentions to Sunset that he knows her because they used to date, she doesn’t correct him by saying their past relationship meant nothing. Plus there is evidence that Sunset was not always a power hungry jerk.  
http://vignette3.wikia.nocookie.net/mlp/images/3/30/Sunset_Shimmer_as_Fall_Formal_princess_EG.png/revision/latest?cb=20130725014635  
This picture from probably her first Fall Formal looks like she’s genuinely happy. And not in the mean spirited way. Now I know she could’ve been faking it, but we’ve seen her faking innocent, and she’s not that convincing.
 
I understand that Twilight and Sunset are very close, but I see them more like sisters. So sibling love is closer than romance love.
 
Just my thoughts.

@Spiritspiral7  
To be clear, I’m not against the Flash x Sunset ship, it’s very cute, but I just want to clarify just how close Sunset is to both Twilights in canon…

@Spiritspiral7  
Well, not really, multiple canon stuff, show Sunset cares more about both Twilights than about Flash. I mean, she writes regulary to pony Twilight, was extremelly happy when she thought Sci-Twi was pony Twilight that came to visit her, and very sad when pony Twilight wasn’t there when she returned to Equestria in Mirror Magic. Sunset just lacks the show of such strong emotions towards Flash.
 
With Sci-Twi, it was evidently shown in Legend of Everfree when Sunset essentially ditches Flash, when she sees Timber, and she thinks he might mean harm towards Sci-Twi. I mean, Flash fans were angry about this, but Sunset just cares this much more about Sci-Twi.
 
This is even more evident in the novel version.:  

 
It’s notable, as people (like on tv tropes or here) say the novel (based on the script) is more shipping Flash and Sunset, but it shows Sunset cares more about Sci-Twi…and possibly that Flash’s feelings are one sided.
 
Another thing that confirms more that Sunset cares about both Twilights more than about Flash, is the Sunset centric “A Friendship to Remember” which may become an episode (the trailer showing the 4 future 44 minite Equestria Girls specials, had scenes that looked as if taken directly from the book)(and the books writer, Perdita Finn also wrote the above mentioned Legend of Everfree novelisation.)
 
For the specifics Sunset, when people forget about her redemption, doesn’t once think about Flash forgetting her redeemption, and hating her, only worrrying about the Human 6 hating her. Showing she’s closer to any member of the Humane 6, than towards Flash.
 
And when she gives up ALL of her memories since coming to the human world, to save the friendship of the Humane 6, she doesn’t even mention grief at forgetting Flash. It’s notable, as Flash was a few steps away, yet she didn’t mention him, or grieve at completelly forgetting him. But she is very pained by the loss of memories of the Humane 6.
 
And at the end of losing memories, Sunset get’s a total emotional meltown when she is about to forget pony Twilight (and thought Twilight would also completely forget her):  
“But the hardest memories to lose were the last ones. “Oh no, Twilight Sparkle,” realized Sunset Shimmer, as scenes of their times together gathered into her mind. “You taught me everything I know about friendship. Don’t forget me! Please! Don’t forget me! ARGH!”
 
(And pony Twilight even wasn’t physically present there)
 
So it if anything,the book shown pony Twilight is the most immportant person/pony in the world to Sunset.
 
And yes, it’s a novel, but it follows what was shown in the series, and it may become a 44 minute special. And everything points out it’s canon.

@BackgroundLoL  
Eh~~_~~/ personal interpretations.
 
Yandere Sunset is ooc already, so that doesn’t really matter. She wouldn’t threaten Flash.

@Spiritspiral7  
Actually, I meant stuff mentioned by movie/series writer on twitter.
 
It’s possible Flash is the senpai, but the position makes a bit vague - which may the intention?
 
To be fair though, it would be rather extremelly OOC behaviour and divergence from canon though, as Sunset is much closer to Twilight, than to Flash, and would never threaten Twilight - and despite what some told, before Equestria Girls, Sunset wasn’t canonically in love, or crushing on Flash, as she told in Rainbow Rocks.:  
“It’s okay. Flash is a great guy and all, but I never really liked-him liked him. I was just using him to become more popular. Ugh! The old me really was just awful, wasn’t she?”

@BackgroundLoL  
Personally I don’t consider the comics(or other sources) as “hard” canon. If something conflicts with what’s in the show, I hold the show as presidence.
 
I personally think Flash is senpai in the picture.

@Spiritspiral7  
Well, she would be in practise, seeing she’ a bit older than Flash and Twilight (max two years accoring to writers, and it was negated by the portal), but in context, she’s Yandere-chan in this picture.

@BackgroundLoL  
Maybe Sunset?

Wait, who is senpai? Twilight or Flash?