My friend is dating one of my good friends but I think she is leading him on because she is always checking out other guys (including his best friend!) and told me she thinks she is just going out with him because she feels sorry for him. I don't want to say anything because he really likes her...

I think it is honourable that you are looking out for your friend, but, I wouldn't say anything.

At best, your information is second hand. It could very well be good information, but you can't provide that as 'proof' of anything.

He may have to learn the hard way that she is not the one for him, or, it could be that she is perfectly innocent and very dedicated to him. Rumours can destroy otherwise good relationships.

I'd take a step back. Keep an eye on him, be a friend when he approaches you.

I would definitely keep my mouth shut. If you were to tell him it could be possible that you'd lose both of them as friends, especially if she were to deny it.

Stay out of it and let the relationship run it's course.

I would not say anything to him but I would tell the girl that you are concerned for your friend and think it is only fair that she be straight up with him regarding her feelings.

Had to spread the rep Artlady, but I agree. A quiet word in the girl's ear might be the best way to go. Just ask her to put herself in his shoes... how would she feel if someone she was interested in was doing that to her?