Can't stop thinking

I'm very new to the forum. I actually never post in forums like these but since I'm going to be up working until I have to go to class anyway, and I can't stop thinking about this girl, and I am in fact completely shocked that I'm successfully completing my circuit theory homework running on practically no sleep and more or less no food (just caffeine) in the past 24 hours, I figured I would take a quick breather and put all of my thoughts on paper, so to speak. If I seem discursive and incoherent then please forgive me in light of the circumstances I just described, haha.

So anyway, I've actually known this girl since the end of last semester. We met on a late-night food run, mutual friends and all that. At first there was no initial attraction for me and I spent the summer more or less not thinking about her. Then the other night I ran into her at a party. We danced for a while and ended up making out on the dance floor. She explicitly told me she was enjoying herself and that she would have left otherwise. Cool, huh? So after the party we hung out a bit and I ended up taking her back to her room and gave her a kiss good night and that was it.

Over the next few days I saw her sporadically. Unfortunately we have no classes together but I saw her in passing now and then, and one on occasion I even stopped to talk to her and she teased me because she had had practically no sleep on the night of the party and blamed me for it. Then once she came and sat with me and our mutual friends during dinner and we flirted more. And then just last night she actually came and visited me at work and since it was slow we talked for about an hour. I asked her to dinner on Saturday night and she said yes.

Sounds cool so far, right? Well, today she texts me and says that she actually had a previous engagement with a friend and that she was really sorry she couldn't make it. Jokingly I told her that she was "really lame." I mean, I made it pretty clear I was joking if there was any doubt to begin with. Anyway, she never texted me back after that text and I didn't get to see her in person that day, either (our classes don't coincide, and my schedule is ridiculously full).

So what's up with that? Does she like me? Did she change her mind? Did I screw up? Or am I just being a pathetic idiot and reading way too much into it?

It really helped me out to type all of this out, in general, and any advice/insight you guys have is awesome. :)