@Background Pony #6B08  
Sombra being bisexual came from a not-entirely serious Twitter conversation with Michael Vogel, which sure…

@AwkwardLuna  

@Background Pony #6B08  

 
We actually have the tweet in question on this site.
 

 
As far as I know it was never made 100% official by the powers that be at Hasbro (like it was for Scootaloo’s aunts), but given that Katrina Hadley was fairly involved with the Equestria Girls series, I can see why Insider might have accepted her word as canonical for the character.
 
I’ll be honest though, I’m still not sure where it was made “pretty obvious” on the show itself that she was bisexual. It doesn’t bother me if she is, but unless I’m completely missing something obvious, I really never saw it myself.

@Background Pony #6B08  
You’re right, I was misremembering

@Background Pony #4E53  
To be fair, it is mainstream media

@Background Pony #6B08  
Slight correction, she started as a storyboard artist before directing some of the later material.
 
@Krickis  
From what I’ve found, Katrina Hadley was a director for parts of Equestria Girls as a shared role. It may be a bit inaccurate to call her the director.

Gender - Woman? Incorrect.
 
Gender - Baconhorse.

@William Flutter  
I was thinking about Sunset being a Recuring Character & not a Main Character, i mean she basicly (IS) the Equestria Girls show. + Race N/A, it should say Unicron & Human.

@AwkwardLuna  
The head storyboard artist for EqG declared she was on her Twitter some time back. Seeing how she had no creative control over Sunset’s character, her word doesn’t mean much.
 
If there’s been another source with some more weight behind it, I haven’t heard of it.

For those wondering where this comes from, it was confirmed on Twitter by Katrina Hadley, the director of EqG.

I’m 100% fine if Sunset is bi, but where did Insider get that info from?

Race: N/A  
How dare they, she’s clearly a member of the bacon tribe.

@Background Pony #4E53  
apparently its real
 
I`m more concerned about both Acid Storm and Knock Out being such, like where in the hell were those two confirmed?

Faker than a 3 dollar bill.