I Need Help/Advice..

So I am kind of open with my sexuality, not fully though since their is a lot of problems I can run into family wise. But this really doesn't have to do with sexuality problems more so relationship problems, i guess? Anyways, I have been dating this girl for almost 4 months on the 1st, I can't say this is the most amazing relationship though. She cheated on me twice, not very open, very secretive, and etc. Now the problem is that I like my bestfriend, but she is straight. I mean she kissed a girl but she said it was nothing and just a test. But to me I don't think she is straight, just the way she jokes around is things a straight girl wouldn't say. Also, they way we act around each other is... I don't know odd. We hug or embrace each other and one time we held hands the whole time while we are in class. I told her I like her and she just smiled, and we kept being bestfriends. But I just find it a little odd on the way how we act toward each other. Maybe somebody could give me some advice on what you think about this, it would really help me out.