How is Twilight supposed to figure out what the cutie map means when it chooses a cutie mark that a bunch of ponies have, and none of said ponies bother showing up?
Sonata Dusk used to have friends. They hung out together all the time and told her what to do, and that's what friends are, right? At least she has her tacos now, and she gets to hear pretty music, but Sunset Shimmer keeps looking at her funny.