A Succubus. Succubi are demons, not female mind you, that can alter their appearance in order to seduce other creatures into doing their bidding. Succubi are often depicted as having wings and small horns, but they typically shape-shift to look like a really hot chick/guy, or even an animal (dogs are easy prey for Hell-Whores; that's why we get 'em fixed).
Use in reference to transvestites and evil girlfriends.
a. Oh, dear, "she" is a Hell-Whore.
b. William has been pussy-whipped by that Hell-Whore Britney.