Talk:My Little Pony Equestria Girls: Rainbow Rocks/Animated shorts/@comment-10390252-20140412171626/@comment-188360-20140412172225

I'm thinking the latter. Looks like Rainbow transformed through her loyalty to the guitar she was shredding with, and Fluttershy transformed through the kindness she showed the hamsters. And if the novel is any indication, AJ will transform through her honesty towards Flim and Flam.