Re: overcome social anxiety... now what!?
Start here for things to talk about and getting over anxiety.
Too bad she has a boyfriend? Why? Now, you have a woman and a man to help you through this journey. He can't be that bad with women, he has the one you want.
Balance both of their perspectives, forget about the woman as anything but a valued friend, seek advice on here, embrace failure, read, read, read, practice, practice, practice.
I have failed more than most men have tried.
Every woman you pass up is a woman you will never have.