She is a bitch. But this is what I like about her. Sometimes is nice to read a history about this type of character.
And those guys aren't good ppl. I mean I think its a pretty messed up thing to have sex with someone who you know has a significant other. Nor do I think that its nice to emotionally manipulate someone by kissing another person in front of them when you know he/she wouldn't like it. I also don't understand why being promiscuous=masculine. But I do agree that's it's nice to read about this kind of character since its refreshing.
You're right in that she has to right to play with other guys. But having that right doesn't mean you should always exercise it. Like she definitely has the right to sleep with guys who she knows have girlfriends, but doing so makes her a bitch. (At least that's the case IMO.)
I don't really think its the fact that she enjoys sex/is sexually active is the reason why people don't like her. It's the fact that she's sleeping with a guy who she knows is in a relationship.
When I was younger I also had asthma, like Take. I missed class for many days and when I came back everything seemed so strange and I felt so out of place that it was scary. so I understand why he treated his friends like that. sometimes you stick to the thought that it would be best to be alone for good