How can I ask her if she supports gay rights without giving it away?

Actually I feel that's an excellent way to gauge how someone feels about LGBT stuff without outing yourself. You have to bring it up very casually as if you're discussing any other issue like abortion or err..the new teacher or anything. It just has to be done discreetly and look natural, and your own response should be carefully neutral or positive in that friendly-straight way

Just keep an eye out for any references to LGBT issues that come up, in the news or class discussion or anywhere around. Also you can casually mention that you have a gay friend for instance and see her reaction to the idea. For instance in the context of crazy/fun things you've done, if you said 'Oh one time I went with a friend in (randomcity) to a gay bar, it was really ...interesting!' - firstly it actually implies that you're straight (since going to a gay bar is unusual for you) but also queer-friendly since you were open to that. If she's straight she would just be curious (unless she's homophobic, in which case she'll look mildly disgusted and you have your cue there ), and if she's not straight then you'll see that she's watching you for YOUR reaction.

Plenty of ways to get some kind of feedback with indirect discussion.

 

I don't know if you've already tried this, but Facebook is a good place to start. Stalk her a little, see if she's posted any gay-related pictures and stuff like that. Also talking about religion may give you a sense of her beliefs. Ask her what religion she practices, if she believes in god, etc. There's a good chance that conversation will segue into gay rights on its own, but if not, you can probably make a pretty safe assumption based on what she says about her religious beliefs. If she doesn't practice much, or especially if she doesn't believe in god, you're probably safe. If she is very religious, you might want to tread lightly. That said, the religion test is not foolproof. I'm sure there are atheist homophobes out there, and there are tons of religious people who love us gays.

 

My Girlfriend went to an extreme catholic high school. However she was very open about her sexuality there and it turned out that more people were interested in getting to know her because of it. She was a lesbian in a sea of homophobic people. However at many christian schools (not saying this goes for your school) most students have never had to come into contact with anyone that was gay. Therefore, they don't know how to react. so i believe that you should continue growing a relationship with this friend, to the point where you feel that no matter what she will accept you. In the end you may even find out that the reason she was uncomfortable with the talk of gay rights, is maybe she is gay, and afraid of being the odd person out. So just continue to get to know her, and when the right time to come out to her arrives give her the chance to ask questions, understand, and accept you!