Affiliate Marketing Secrets

I am a sophomore in high school. I am fifteen. (That wonderful age where the most irrelevant dramas take up 90% of your mind and ruin your day) I am a lesbian, and their is a girl whom I really like.
I have never had a girlfriend, (and neither a boyfriend) so I am a little clueless on how to approach her. To make matters worse, I am not even sure if she is gay herself. She has that gay air about her. You know, that homosexual energy. She does dress slightly masculine, (which I understand really says nothing about a person’s sexuality) and her hair is cut short. I know for a fact that she is single, and she does support gay rights, the main question here is wither or not she is gay herself.
She is a new student. (junior) She has only attended my school for a couple of weeks now, and she still has that “lost” attitude a person has when at a new place. It seems as if she has not found a group of friends or niche, so this really is the best time for me to make my move. I would just go up to her and strike up a conversation, but I am afraid that at this point it would too awkward. You see, for the past couple of weeks she and I have been sharing these odd glances at each other. I am unsure as to how to explain them. It is as if their is something hanging in the air between us, yet it may just be me imagining things.
I am simply confused as to what to do or how to approach her. I have lunch with her, and I have one class with her. I am just too afraid that she is going to be weird-ed out by me. What do you suggest I do?