I like this girl, but I don't know if she likes girls. What should I do?

I'm bi and I have a relatively close friend that I am really into. I know that she has no problem with same sex couples, but I'm not out and I don't know if she is into girls. I'm afraid that if I tell her I like her I will freak her out and she won't want to be my friend. I know that is a silly thing to think, but it's true.

bring up the fact that you're bi around her somehow, see how she reacts. normally when ppl are also bi/lez and I bring it up they'll be all "you're bi? me too!" if she doesn't say something like that, then she's probably either in the closet or straight

You also can start talking about bisexuals and see what she thinks.
Without letting her know you are, so you are protected.

If her views points are good than you most likely can tell her
if it's bad well don;t

Than again some people will talk good about that and if they found out you are than their might think bad, so it's another change to take.

It's in your ball court. I am sure if you talk about it and feel it. It will have good turn out.

Always leave yourself a road for recovery. You could jokingly say, "I don't know if I like girls or boys but if it turns out to be girls, you'd be the first one I'd hit on." If she sounds negative then you can respond, "I was just kidding. I like boys" so nothing's lost.