She told you to piss you off, plain and simple. Not to rain down on you or anything, but hasn't she already slept with this guy she supposedly has a crush on? If she keeps going on and on about how she had a crush on him, she's already slept with him dude. (I'll tell you if my wife comes home night after night talking about how she has a crush on some other guy while she was living with me and being supported by me her ass would be out on the street so she can be with her special guy.)
She just doesn't have the balls to come out and say it. And from what you've been writing in this thread, (and please tell me if you think I'm wrong because I don't know you personally) I don't think you two will be getting back together. So in that retrospect, I would'nt worry about you hooking up with a girl at some party. I'm willing to bet it made you forget about her and it helped you to realize that you have to move on and this chick made it a little easier for you. Personally, I wouldn't lead her on or anything because you're still on the rebound but I'm still willing to bet it did make you feel better.