[Sackett]

What I think is interesting is that she labels herself a Tsundere. How many people do that?

I think it's pretty clear she a Yangire (not -dere, since it isn't love troubles that made her crazy), and her way of dealing with it is by labeling herself a Tsundere. because Tsundere's aren't hated for acting crazy and violent- instead it's expected. (A not so subtle Take That against the whole Tsundere is moe craze).

Of course, by episode 12 I think it's pretty clear that she's starting to get better. For one thing instead of showing off her body and acting like it's no big deal she's begun admitting that she's really messed up inside, particularly being scared about a physical relationship. (Which is probably why Araragi is sticking with her, he's got a Messiah complex and he can tell she's the person who needs him most). She might be turning into a Tsundere- maybe it's even deliberate- maybe she's channeling all those negative feelings into behaving like a Tsundere and teasing Araragi, since he puts up with it.

I find her a fascinating character. Never know what she's going to do.