Look, right now you're coming from a position of pathetic weakness. Of course she can make you feel guilty. She could make you feel anything, and if you want the truth, she'll probably keep you in this state as long as she can because girls like to feel like they're holding the reins.
YOU need time. Tell her. Don't see her for a couple of weeks, don't get anywhere near her on Myspace, don't even talk to your mutual friends. This is a power struggle. Do not lay down in front of her with your belly up. Don't tell her you'll always be there for her, bla, bla, bla. Tell her you don't know right now and you need time to think.
And then actually take some time to think. You're not going to miss out on some grand opportunity if you don't talk to her for awhile.
It's not just a game. You need to treat yourself with more respect than she does, for your own sake, no matter what the outcome.