Cathy.
What sucks about her is that while she herself seems essentially powerless, she might have some big backers. Of which she's threatening me with. I wish we could ask Lindsey more about these Senior Partners and how powerful Eve actually is.
Oh - it's no excuse. I just think that's her motivation. I think she desperately wants to be in the cool crowd. Knowing people's motivations helps me when I fight. Not that most vampires have very complicated motives. They're generally half-brainless.
I agree that she seems ruthless as hell.
Then maybe we should steal them and throw them in the ocean. :D