In the eight-issue comic Batman: White Knight, is revealed that there's has been two harley quinn's
. The first one abandoned Joker after years of abuse and realizing that he only true loved batmanThe second
Harley is the one
who started wearing those lewd outfits and acting like a murderous crazy psycho.
After Joker becomes sane, second harley gets all mad and becomes the neo-joker in hopes he comes back as the clown criminal