I think my crush likes my best friend?

I really really like this boy but I am worried that he likes my best friend. She is the best friend you could ever have: she is fun, understanding and always knows how to make you feel better. But she talks quite a lot and I am worried that if I tell her who I like then she will accidentally blab it. She is very pretty and loads of boys like her. She's also a bit of a flirt, although she can't help it. My crush is really funny and always makes me laugh. He teases everyone but when he teases me, it's never mean in any way. He doesn't tease her. She told me the other day that she thinks he likes her(she doesn't know I like him) and I was like "oh yeah" and stuff but I felt awful. And then a few days later she said that she'd noticed that he looked quite good.

I don't know what to do Should I tell her I like him and risk him finding our or should I just go along with it. I'm way too shy to ask him out or anything and I am scared he will reject me. I'm not a jealous person but I think that I'm jealous of her and I don't want to be because she is my best friend. He's said before that he likes me(like as a friend) and if he sees us together on the street he always comes up to us but...