I think I am a bit older than most of you guys, mid thirties. And I am kinda new to gaming girls, so take it for whats its worth. But if there is one thing I have learned its just be direct, sure its scary, sure you may lose your weed buddy, but it clears you up for whoever is next.
I was in a similar situation where a girl who I was interested in, we would see each other every few weeks. I knew she has a boyfriend, and I truly enjoyed her company, so I was was not trying to put the moves are her at the time. Then she confessed to me that her boyfriend had cheated on her. That switched me into the mood its time to make the move. So i said well he farked up, and his turn is over. I am going to take you to dinner and show you how a man treats a woman.
She was taken back by how forward it was, and how much confidence I had in the statement. All it took was telling her what you want, and telling her what you are going to do. Its pretty simple really. And if she is reluctant, move on, never say sorry, never ask again. Just move on. She will do two things, feel she like wow that dude is not chasing me, and come back to you, at which point you have to stay firm, its going out or the highway. And if she does not come back, or does not want to date, then well you know where she stands, and you wont have to be guessing anymore if she is into you or not.
Once I have found the next girl or girls I am in, I am fine going back to the girl who rejected you, as you can never have to many friends. But just dont go back until you are ready to actually be her friend, and treat her like a real friend! Don't do anything for her you would not do for any of your guy friends because that is all she is going to be for you.