I know I commented some time ago, and this is old, but the “A Friemdship to Remember” book, pretty definitelly shows how unrealistic this situation is, as it shows pony Twilight, is incomparably more important to Sunset, than Flash, and would never date or have any romantic relation with Flash, if she thought Twilight still feels anything towards Flash.
 
It’s notable, as the book 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 that the book was writen by Perdita Finn. Perdita Finn wrote the Legend of Everfree novelisation, were people say there is stronger Flash x Sunset chemistry, than in the movie.
 
But it’s visible, from “A Friemdship to Remember”, the feelings are one sided, only from Flash - 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.
 
And when she gives up ALL of her memories since coming to the human world, to save the frendship of the Humane 6, she doesn’t even menton grief at forgetting Flash. It’s notable, as Flash was a few steps away, yet she didn’t mention him, or grief at completelly forgetting him.
 
She get’s a total emotional meltown when she is about to forget pony Twilight (and thought Twilight would also completely forget her), which almost comes of as if an interrupted Anguished Declaration of Love  
“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)
 
Again, you can ship Sunset and Flash - it’s a cute ship - but I just note how extremelly unlikelly this scenario is, even if one has characters as comedic sociopaths…

@Background Pony #D6A4
 
I don’t thinks so.
 
By the huge amounts of rage Twilight is feeling, killing them would be too merciful for her.

Twilight’s gonna kill those traitors.