I have to disagree with Carmen in that you should tell her you'll be there, but take a step back. Doesn't the words not match the actions? It doesn't make sense. Don't give them the option of getting back together, if that is what she wants, then she has to live with the consequences of that.
It sounds like you guys are very confused about how you feel and you have to look at the actions you have done as well. You felt she was going too fast but then you tell her you love her and spend all your time with her? I know you want to be that great boyfriend and do all the good things like the perfect dinner and perfect dates and all this great stuff, but if you don't feel the same way as she does, you shouldn't be doing that because you can't keep that up forever. I just found that to be a bit contradictive.
But yeah, they are right in that you need to break off contact completely with her, even though you care and want to be there for her. Why do you think the decision hasn't happened when you guys are still talking about it and acting like you are together? Aren't you a little angry that she gave into another guy's advances and found it "passionate" and "attractive"? Is this relief for you as maybe it was getting more serious than you wanted because otherwise you'd be pissed about it.
You need to be on your own and be brutally honest with yourself about what you and her are both doing. It helps to do things that make you happy but you want to have a serious understanding about everything so that you can really grow and learn from this as a person. If she wants to talk in the future, which she will, you will also have some wisdom to impart to her. But as I say in all my posts, you don't need her to be happy. You care about her, you think about her and that will not go away anytime soon. But you don't need her. You want her in your life to make you more happy, and how can she when she is confused. This is what she wants, you cannot meddle. Focus your energy into postive results: gym, schoolwork, friends, all of that. You will be a better person in the end.
Waking up next to a beautiful girl,
Step outside and say hello to my beautiful world.