ive never had a problem talking to guys because, in addition to all the girly stuff i like, i also love to play videogames, shoot paintball, and ride 4- wheelers.
just act confident, but not cocky, around her. if you had more time, you could just casually talk to her a little each day, ie make funny comments about the teacher, your classes, upcoming tests. thats what i did with the guy who sits next to me in biology and we are great friends now. but you can manipulate it to just get a foundation and base with her, and work your way up to where you can feel confident enough to ask her out.
just dont act all nervous and akward around her