For me its Lola. She is the hottest and definitely knows how to manipulate the boys. Almost like a female Gary; it would've been interesting if they had gotten together, she would be a Lady Macbeth type.
Second place would go to Mandy. She seems like the typical cheerleader but becomes more interesting later on. And she remains loyal to Jimmy in Chapter 5.
Zoe is okay, I think she would've been better if she had been introduced earlier and she had been fleshed out somewhat better. I found Pinky and Beatrice to be annoying, the standard stuck up rich bitch and homely nerdy girl, respectively. Anyway, that's just my opinion.