This might be tough. And it’s here that my theory ends because I couldn’t think beyond this. But for my theory to work, yes. She will need to find or have already made new friends. After all, she would have had spent her whole life in the Mirror World.
If my theory becomes reality, Hasbro/DHX (or whoever is in charge) will need to come up with something cool for Equestria Academy. New characters that will not be mounds better than the Mane Six, but not dull, flat characters either.
Maybe Sunset Shimmer left Canterlot High and transferred to the Academy?