OK there is nothing you can do since you are shy! If you really really like her then you need a game plan.
First read up on the book "The Game" by Neil Strauss, then if that's not enough read up more on "The rules of the game". Hurry, order from amazon now. While you are waiting for the book, read this forum:
link Then come up with a game plan, and go somewhere, I used to live in Rome so it was easy to travel an hour to some clubs I don't frequent, and practice on as many girls as you I find. The reason for this is you won't fear the rejection, who cares. the people there don't know you so you will be less shy!
Follow this advice and within a few months, you will probably be thinking. hmmm. if I can approach all these girls, why the hell bother with that girl!