Getting really mixed signals from the girl I like. Please help me!!?

[dbh]

First of all, we are both seniors in high school. I have liked her for about a year, and we are good friends. Whenever we see each other in person, she acts like she likes me, but I always have to text her first and she hasn't been continuing the conversation very well lately. A few weeks ago was registration for school and we were waiting in line in the auditorium with a bunch of other kids. She was down by the stage and I was far away from her on a different level. I was turned around when she yelled my name across the auditorium and waved at me to say hi. My friend has been trying to tell me I should give up on her and that girls want what they can't have so I need to pay even less attention to her. Last week at the school football game I was leaving and walking past the student section when she shouted my name like 5 times trying to get my attention. I didn't look at her and just kept walking. I felt bad when I got back to my car so I texted her saying "hey someone told me you were trying to get my attention when I was leaving. What's up?" and she never replied. I'm too scared to tell her how I feel because I'm pretty sure she has a thing with some other guy but I'm not sure. I like her so much so please help. Why doesn't she text me but then act all flirty when we see each other in person? Also, i'm pretty sure she's figured out that I like her by now. I just wish I could find out what she thinks of me. One last thing. A few months ago her friend hacked her twitter account and tweeted some flirty tweet at me saying let's get jiggy or something like that. Maybe her friend knows she likes me? Any opinions are welcome.

[jUA]

If you really are good friends with her, you should be able to have a serious conversation about it with her, and that would be the first thing I'd do in a similar situation. She may like you back but also be hesitant to admit it to you.
You may also consider just not starting anything with her at the risk of losing her as a friend.
Without seeing any real interaction, it is hard to give advice on this kind of thing. Best of luck in whatever you decide to do!