Keep us updated. We like to live vicariously through other people...
Seriously though, I agree with Karen, though I think it is more likely that the situation is case #1. She probably still loves you, and loves being with you because it feels good having someone to love and someone to love you. However, she isn't ready/willing to commit to being with you exclusively. She probably isn't even looking for someone else, but she is afraid of committing at the age of 22.
You can confront her and give her the choice of being your GF or cutting out all the physical stuff and going back to being friends. OR you can tone your actions WAY back and see how she responds. I bet if you withdraw she will come after you, and you may be able to swing getting laid, if that is what you want.
The two tactics are very different (obviously). Having the conversation is much riskier, as it could drive her away, or even if she commits, she could resent the fact that you forced her into making a decision. On the other hand, it could be just what she needs to snap out of it and grow up. Hearing "make a decision about the status of our relationship, or I walk" could have a big effect on her.
Withdrawing from her could have the desired effect of bringing her closer, but this sort of thing would drive me NUTS. I would constantly analyze everything she said and did, looking for clues. Also, you would have to put yourself in the passive waiting game of letting her come to you to ask for a change in the status of your relationship.
I've used both tactics, and if you can let go and just not care, the second is far more effective. If she really wants you, she'll start chasing YOU, and that is a fantastic thing. Eventually she'll bring up the topic of your relationship, and you'll tell her that if she wants to be your GF, you are fine with that. Be cool, you are the older, more experienced person in this relationship. You can pull this tactic off, if you have the patience. Now, if you withdraw and she does the same, and the passion cools, then it wasn't meant to be and its time to find someone new.
Good luck!
Ryan