Be confident, ALWAYS. Act kind of like an asshole, not in a negative angry way but in a funny way. Poke fun at her. Another trick is to talk to her as if you have no intentions of getting with her, like you're talking to just to make conversation. It takes the pressure off in your mind.
Sometimes I walk to up to one and burp loudly. She has no choice but to respect the courage it took to do that.