Here's what I think you should do. Go out and date another girl, the one your friend doesn't know. Then next time you and her hang out, casually mention the new girl you're seeing. Chances are, the girl you're friends with will get curious and ask you questions. Maybe even get a little jealous. But most importantly, she only likes you as a friend (for now, at least), do I don't recommend making any moves yourself. Let her initiate it first. But don't wait for it, go out and try to meet other girls instead, the ones who will like you romantically.