You're 17 - live your life, why are you getting into such a complicated relationship? Find someone you can have fun with, someone you trust. If you really want to be with her, then you're going to have to stop the nasty comments and try to be a bit more secure, I don't know how to advise you to go about trusting her again though - she cheated and that's big. She sounds confused and it's like she's pulling you into a path of destruction. It's not a good relationship to be in if you ask me.
To love is to suffer. To avoid suffering, one must not love; but then one suffers from not loving. Therefore, to love is to suffer, not to love is to suffer, to suffer is to suffer. To be happy is to love; to be happy then is to suffer, but suffering makes one unhappy; therefore to be unhappy one must love or love to suffer or suffer from too much happiness. I hope you're getting this down.