Why Is She Doing This?

I have a friend (girl) and I don't know how she thinks of me. Please do not give me false hope for anything, I want honesty. If I walk into a room she usually waves and says hey but not always. She sometimes comes up and gives me a high five and briefly talks. During our school day (we are 14) I only have 1 class with her. However she usually won't just start convorsation or something if we are on AIM. If I go into an AIM chat that her friends are in she doesn't say hey or even really talk to me. Our convorsations are usually brief, I'm not sure if it's because we don't know enough about each other or what. In the one class we have together she tried to invent a sign language thing so we could talk to each other without getting caught by the extremely strict all hearing teacher. On things that ask to list 10 people that just come to mind so you can answer questions about them, I am usually not on there. However, I am fairly high on all of her top friend things.
I somewhat like her but really I just want to be better friends with her. I don't know what to do or why she is doing any of this though. She is usually pretty confident with all of her other friends, however I am shy. Like I said, she doesn't completely avoid me but I seem to be better friends with all of her other friends. Like today, I was standing in the breezeway, and she was taking pictures, then I heard one of her friends say take a picture of me but she didn't. She randomly called me today saying "Hey baby what's up?" Then her friend screamed and the phone hung up. She called back a few seconds later apologizing for the hang up because her friend grabbed the phone and hung up thinking it was her other friend with my same name. Like I say I don't know what to do and I just want honest opinions. If you could all please give reasons for all of these things that would help so much. Sorry about the long message and thank you for reading and answering.