Well, don't take this as gospel, since I have quite a bit to figure out with her.
I've mentioned before that regular Kit has a personality summed up by :3, Goth Kit on the other hand, id say is a mix between the personality of the goth kids in South Park (ie: always acts miserable, probably listens to pumped up kicks) and Nicole from Class of '09 (ie: narcissist, acts like an a-hole to anyone she sees, drops an f-bomb every few words), with a tiny bit of regular Kit's personality