>>42773658
>>42773939
I suggest you give Forgotten Friendship a try. It's only 40 minutes, it summarizes the movies to get you up to speed, half of it takes place in Equestria with Sunset as a pony and it also ties up her arc with Celestia.

https://youtu.be/5Joy4wlZ8lk?si=4pB0KcVCbYjtDiQW

If you'd like to quickly check the one-shot comic that reveals Sunset's backstory, here it is:
https://www.tumblr.com/wolfnanaki/98020387412/the-fall-of-sunset-shimmer-the-official-comic

>>42686106
Thanks Lemon Smash