Sunset Shimmer: Oops..., my bad! Let's just pretend all of this from the first EQG movie of me being reformed in a infamous worse way possible never happened. sigh It's great to have the old me back..... and it also feels so delicious [Switches from gentle and friendly to full-on psycho] TO DESTROY!!!!!!!!!

Sunset Shimmer didn't like the ending of Equestria Girls (2013) that much, she just wanted to remain as a evil, self-centered, cynical, callously psychopathic punkrock bully-of-a-girl forever, but there's nothing she can do about it.
Now, Sunset decides to do something that's going to make you wish you've actually know what the whole half-baked redemption thing really is.
That, my friends, is how to ignore the infamous redemption and pretend like those scenes never happen.