Sunset Shimmer's entire world collapsed overnight. It did it without her even noticing. Upon finding out she has no idea why, and neither she nor Princess Twilight can figure out how it's even possible.
All she knows is that when she met her friends the day after, they weren't her friends. When she meets other students they still hate and fear her. When she tries to remind people that she's changed, they don't remember any of it, but they do remember all of the bad things with crystal clear quality.
Everything she regrets --from being a bully, to being a monster, to yelling at Twilight during the Friendship Games-- remains. Everything she's proud of is gone. With the entire world convinced the truth is a lie, no friends amoung humans, and time running out, Sunset races to understand, and hopefully fix, whatever has happened.
Meta Notes:
When A Friendship to Remember came out I remember being extremely underwhelmed. This is my attempt at taking the basic story and making it whelming.
Well, most of it. You see, most of the book (Chapters 3 to 23 of 23) is the official prose version of Forgotten Friendship, and that is the story here. I feel like the story, at its core, has some real potential, but it did not live up to that potential.
This is a straight up retelling, that means that while it is AU it isn't divergent. More . . . parallel. It doesn't spin off in a different direction, it just tells the same core story with different execution and details.