Sunset doesn't know what she expected from the snap decision to go back to the town where she was born. It certainly wasn't this.
People left and right knowing her name.
Somebody pretending to be somebody pretending to be her.
The apparent existence of a world of magic and unicorns.
And in the middle of everything, a girl who looks like her, sounds like her, and has stirred up a whole mess of trouble and drama just waiting for anyone who happens to be named "Sunset Shimmer".
This is an Anon-a-Miss story, which means that it takes the 2014 comic My Little Pony: Equestria Girls Holiday Special as it's jumping off point. As is generally the case, if I write this properly it should be self-contained and thus completely accessible to people who have never read laid eyes on the comic.
The idea behind this story is that the point of divergence from the comic is human-Sunset's arrival, and that is the whole of what has changed from the original premise. As a result you won't see many of the the things that have become common in the genre as a result of the influence of Dainn's version (the sirens showing up, things escalating severely, Gilda, so forth.)