I have a bf gf situation?

Ok I am friends with a person on twitter who follows this girl who I like. She follows him too. She follows other guys too. The person i'm friends with hangs out with her. I think they are boyfriend and girlfriend. Not sure though. I asked if they were going out and he says she does not want me or any of her friends to revel if she has a bf or not. I tweeted him again replying to one of his tweets saying. "Your girlfriend (insert name) would like that" and he said "your making an accusation." He never said if it was a false accusation or true. Then i said you should change your profile pic to you and the girl. He said "then people would think were going out." He's never really says direct that they are going out or not. How do I get him to revel if he's going out with her. It has to be sneaky.