or keep in touch as friends and when she breaks up with the other guy, you'll be there ready to pick up the pieces.
but don't do anything yourself to bring about that result(the breakup), as that would be bad karma(or whatever underlying universal principle that you choose to believe is at work)
and if that never happens, and she is happy, you can be happy for her. after all, if you care deeply about her, that's all that'll matter.
and in the meantime you might meet someone new that stirs the same feelings, for there are plenty of people out there, and you'll know from experience not to miss your oppurtunity.
maybe she'll have some cute friends to set you up with
