Hi Joe
It may seem strange that you used to be comfortable around her, yet now you feel shy, but it's natural, really ~ you used to be friends and now you see her as 'a girl you are attracted to', so it's different.
However, she is not different, and you are the same boy you always were, so take a deep breath and try to remind yourself of these facts before talking to her. Pretend to yourself that you still just see her as just a friend. Otherwise she may wonder if she has offended you or something.
You asked her to go bowling ~ if you were confident enough to do that, then why not ask her to go somewhere else. I presume she said yes? If so, then she may think that after that one 'date' you don't enjoy her company so much.
She is a girl; a friend; you like her and feel comfortable with her. She is only human; she's not a dragon! Talk to her ~ don't lose her!
Good luck!
