First of all brother relax. She is a girl, not a monster.Well its normal and sometimes if you act all nervous, girls find it cute. Look first of all you have change your attitude; stop thinking that she is the only one in the world. She is girl, a normal girl. Do you watch movies? I think you do.Okay, so you must have seem absolutely average guys going out with hot chicks and this doesnot only happen in movies. You can see these kind of examples all around you. So be yourself. You know that, you'll make it. Just go and talk to her, atleast say hi!!! If she is so "cool", then you will have no problem dealing with her.
and one more thing, when you get nervous, breath deeply.