“Nervous to talk to a girl”

There is this girl in my guitar class at highschool who I like but am to nervous to talk to. It is about halfway through second semester of grade 9 and if I can’t get the courage to talk to her then I probably won’t be able to ever be with her. I do t think she notices me except for during the playing tests where only one person plays the guitar at a time while the rest of the class watches you. I hate being watched by to many people at once and yet she doesn’t have any problem with performing for playing tests and if I show fear then she will just think of me as a coward and never want to talk to me. Both her and I where invited to join the guitar ensemble/band which was a great opportunity for me to get closer to her but I declined because I am an idiot who is controlled by his fears. Please if anybody could give me even a little advice to look like more than just another person to her I would greatly appreciate it.