Define 'seeing'. Does it mean that you just hang out as friends or does it refer to something a tad more physical? If it's the former then it's the classic do I ruin the friendship by asking for more scenario - I mean, she either just views you as a close friend whose company she thoroughly enjoys or she is in fact quite fond of you but too scared to test the waters in which case I would give you the green light and say that you should just pluck up the courage and tell her that you like her, you know, as more than a friend. Just put it out there if you are willing to risk the friendship. After all, life is about options, and by telling her how you feel you are providing her with another option. As long as you are just simply stating your intentions, and not demanding and harrassing her to choose, well it's a-okay according to moi.
However... if it's the latter, that you guys are already sharing some form of romantic intimacy then well, sorry to say but you are just playing second fiddle to her real, actual boyfriend. If she wanted you then she would have ditched him, it really is that simple - sometimes things really are just black and white, we complicate them by adding shades of grey. And besides, do you actually fancy sharing your woman, going halves on her with some other dude? Go get yourself a whole woman I say!
[SIGPIC][/SIGPIC]
Love is like a merry-go-round: you get all dizzy, and then you feel sick!