I assumed its an attempt at a cool, I-don't-care-if-anyone-likes-me character.
The problem is that type of character is weak and in no way cool. Especially if they appear to have no redeeming qualities and are just an asshole all the time. But if she is called out I'm sure Willis' fans will defend her with "you just don't understand her!".
Sal and Carla have the same sort of shtick but it has been shown that they both have some other facets of personality.