How do i pop the quesion?

I think that it's wonderful you've known her for so long. Congratulations on feeling so in love. It can't hurt to start thinking of ways to ask her, but before you do, take a step back. You are 17....she is 15. She can't even drive yet, neither of you can vote yet, I ume neither of you live on your own or can take complete (and financial) care of yourselves...you are too, too young. Start a journal of great ideas to keep the love alive and propose to her SOMEDAY - then, when the time is right, you'll have hundreds of perfect ideas and can build them into such a meaningful proposal.