Angry & Confused

I don't know about myself sometimes. I need some help. Last February, for some reason unknown to man, I made myself a new friend. Between then and June I ruined it. Here's the story:

I don't know how, I don't know why, and I don't exactly know when, but someone came into my life that would die to hear me speak. In the hallways at school we'd laugh and joke around and just have a damn good time. Her friends noticed a change in her personality when she was around me they said. She was "all happy and giddy and skipped and huggy and was never like that before." Whatever. So, we became pretty close, talking everyday after school and hanging out here and there. It really wasn't a bad setup to tell you the honest truth because I could just be myself. All of that changed on a group trip to Italy this summer and it's becoming a night mare.

After having her sleep on my shoulder through a 7 hour plane ride, quite a few 3-6 hour long bus rides to airports and hotels with conversations that made us laugh, cry, and all the in-between, she stuck me with her old friends and then ignored all of us. It didn't really bother me because I'm not clingy, so I let it go until the end of the trip when I found out that she was talking behind my back. I'm 17. I know how to handle myself with people who talk behind my back, I've reamed people out before, but this one was a shocker.

On our flight home we conveniently had engine trouble and were stuck in Frankfurt Main for the night. Being as pissed as I was I would have dragged her by her hair to my room like Brave Heart, so I had someone send her to my hotel room where I asked her what she said and she lied straight to my face. I didn't publicly scream at her and I thought I handled the situation maturely, but when she lied, it ended everything. I'm a human lie detector and I have no patience for people like her so I put her in her place, made her cry, and threw her out of my room…the whole bit. She came back and made some pathetic apology that I rolled my eyes and accepted because I just wanted to get home without any drama. Everyone was at each other's throats anyway. I went home and set her up just like she did me, which I must agree was immature. I figured I'd talk behind her back and let it get back to her. I told her best friend that she really pissed me off and was completely ignorant (basically what I told her straight to her face in the hotel room so it wouldn't be such a shocker), and just as I planned it got back to her and we haven't talked since.

Now, I don't know what her issue is, but she seems to be looking at me an awful lot at school. Now her friends say she doesn't care about the situation, but there's something off about the whole thing. I know this may sound stupid as hell, but it bothers the **** out of me. Somebody tell me what the hell is going on and if I should just continue on treating her as if she doesn't exist?