What should i do to win my best friends heart?

So there's this girl and we've been really good friends for probably 4 years now. Im an upcoming junior in high school and so is she. A couple weeks ago we were talking and it lead into a discussion about how we both had deeper feelings for each other. We started hanging out more and it got to the point where we were always holding hands, kissing, and making out(not publicly of course). I felt like things were going well until she went to a party and made out with another guy. We had already discussed our situation and she didn't want any official relationship so I said she could do whatever she wanted to. She said that didn't seem right and insisted on promising me she wouldn't hook up with anyone else. But like I said before she broke her promise and made out with some other guy. The next day she told me what she did and was half sorry and it ended up that she wanted a break. I reluctantly agreed because I can't force her into a relationship. But she said she still had feelings for me and that I was treating her perfect. So we would just be friends for the moment. Whatever. However, yesterday I was with at her house watching PLL (fml I just wanted to see her) and she was all over me leaning on my shoulder putting her legs on me holding my hand forcing my arm around her kissing me on the cheek and I kissed her and she insisted that she didn't kiss me back but it was obvious she did. I am falling for her more and more everytime I see her but she says she doesn't want a relationship and is very decisive that she only has some feelings for me and doesn't want to force anything even though "im perfect" . She's very hard to figure out but I want her to be only mine and not cheat but she kinda wants to hook up with people most likely cuz its summer and there are parties and she likes to drink. Basically I want to win her heart. I know im basically falling in love with her and I think about her all the time (at 2:15 EST) and so I need suggestions on what to do next.please