<human>: Condense the text into a few key points

She used to be a good friend of mine and cheated on her ex with me last November. We've basically been dating since January. Now I say basically because she says she doesn't want a relationship, even though we talk, act, and basically are together. 

Last February she went through my phone without my permission and found I had drunk texted my ex one night after I told her I hadn't talked to her. He has used this against me since then and has been manipulating me to justify everything she does that's bad, like make out with other guys cuz "we're not actually together". 

The problem is that things can be so amazing at times and then all of a sudden she'll get mad that I've lied to her and then they go to shit. And just when I realize it she acts sweet again and it goes right back to being well. She's also gorgeous, a 10/10 while I'm pretty average. The sex is great too but she says that she could have anyone and that I'm lucky to have her. 

Well I'm home for the summer and can't see her and the last two nights she's brought guys back to her apartment planning to have sex with them, but crying over me before it actually happens to the guys and says that they didn't have sex so its ok. I can't take it anymore and feel like an idiot. I'm talking to her later and I know she'll find a way to justify it and make it seem ok.

I want to end it but best friends with my best friend's fiancee. I always see her when I'm at school and can't escape her. I just don't know how I'm going to be able to go through with it.
<bot>: girl that I'm with continues to manipulate me to believe that everything is ok with us despite her treating me like shit and I don't know how I'm going to end it even though I need to.