My Little Pony: Equestria Girls: Through the Mirror (Equestria Girls, 1)

"When her new crown is stolen from the Crystal Empire, Princess Twilight Sparkle pursues the thief, Sunset Shimmer, in an alternate world, where she finds herself turned into ... a girl! To regain her crown and return to Equestrian, Twilight must learn to fit in in this strange new world and defeat Sunset Shimmer in a competition to be crowned princess of the Fall Formal at Canterlot High. Luckily, she has the assistance of Spike and five girls who remind her of a certain group of ponies back home"--Provided by publisher.