Going back to the OP:
I agree with a lot of the advice on this thread. UGA is absolutely right in saying that you don't want to be the one who caused them to break up. It doesn't give much credibility to you and you look like a pansy (for nice words sake). Be a man and let everything be. I'm a firm believer in whatever's supposed to happen will happen, and that everything happens for a reason. Maybe she's been with this other guy and it will show her how good of a guy you actually are, in comparison to him. On the other hand, there is a chance that she will never see you as anything more than a friend, which is ok too. I've never been big on becoming a friend and then dating, because you're then risking a friendship. Personally, I would let the two of them fall apart on their own, and be there for her if she needs you, and then gauge her interest carefully. If another makeout session ensues, chances are she's into you or she's drunk. So be careful, but I'd stay back. If she doesn't come to you, it's just not meant to be right now.