Maybe she didn't realise you were trying to hit on her. Or perhaps she did, however felt you were being incongruent (how many people get nervous just being friendly with someone?). Did you really want to 'continue the chat' or did you want to take her in the locker room and fuck her ass ? Obviously verbalising the later is probably not a great idea (although why not) however maybe you just need to show some more intent (...be authentic).

You were nervous because your current perception is she has more value than you. You need to work on improving yourself.

Overall talking to a girl is good start and further than some guys get. Keep doing it, lots.