I was thinking today, "What if I told her I was gay?". She's a girl in my class and amazingly shes already had a bi friend come out to her so I figure she'd be understanding. I just was wondering what pros and cons people could think of on the subject. For me it was pros: someone to talk to, somebody knows, I could (possibly) meet her bi friend, and its less awkward since she's a girl. and cons: stops being my friend (couldn't see why), or tells the whole school in a mad frenzy of gossip (I don't think she'd do that either)
Is she a somewhat close friend? It might be a little weird for her if you two aren't close and you come out to her. If she's a somewhat close friend and you think she'd be supportive and you feel comfortable having someone else know, then go for it. The first con is 99% unlikely to happen. As for the second, that's a risk you have to take with any friend when you tell them anything.
If you are fairly close to her, I would say she sounds like a really good person to talk to. It is nice to have someone to talk to about this stuff (that is why this place is amazing) but it makes a difference if you actually can speak to someone face to face. Good luck!