Nothing wrong with that man. While I know you are a nice guy and you know you are a nice guy, she probably just took it as coming on a little strong. I mean you guys were just on talking terms and you were giving her tickets and buying her gifts? You did it out of the kindness of your heart but she probably took it as you wanted something in return. Hence her feeling uncomfortable. Girls get guys coming at them all the time they are always on the defensive. Talking to her roommate of course got back to her and it sounds like you are really trying very hard. Girls for the most part just aren't attracted to that. They want to be the ones that like the guy first, and then get swooped off their feet.
What's your intentions here? You thought you were making progress...towards what? A relationship? Hook up? How well do you even know her? Do you just talk to her in class? I would take it easy here and slow down on what you are doing. Don't ignore her, but when you run into her still be friendly and nice for a little while. Ask her how she is, make small talk and when you hit that lull, leave it as it is. Slow it down a bit, be patient, and when you are getting the positive vibe again take it from there. This could be a while (month, couple months, etc.). Hang out with her outside of class and really get to know her and have her feel comfortable around you.
I remember I liked a girl and she actually liked me at first. I came at her too strong with lots of (drunk) texts and asking her to do stuff because my friends told me too. If I was patient, it could have worked out. You gotta be too.
Don't worry about who she is hooking up with and so on. There isn't really much you can do about it. My ex's new boyfriend looks like a tool but if I went to her telling her about it, she isn't going to listen. Respect what she wants and she'll make the mistakes on her own. When he ****s up, you'll look better in comparison, trust me.
Waking up next to a beautiful girl,
Step outside and say hello to my beautiful world.