In fact, she simply applies some minor cosmetic changes to her costume, like a stylized (bat-like) letter M instead of the batwings, and a denim miniskirt, and renames herself Misfit.
The actual transformation involved making some subtle cosmetic adjustments to her costume, like replacing the batwings with a stylized (bat-like) letter M and swapping it for a denim miniskirt, after which she gave herself the new identity of Misfit.