Then talk to her again ALONE without him and ask her to please tell you what is going on. Tell her that you have an open mind and just want the truth. That if HE is crushing on her, then you need to know..That if she is crushing on him, you want to know..That if they are having an inappropriate friendship, you want to know the truth no matter what..
P.S. - When my GF finally told him that she was not interested, he got more aggressive, hoping that she would go to him if he "worked harder". I need not tell you how that went..
My guess is that some think he will change but the majority is just looking for the same thing he is. So I don't think he is leading them on but I still wouldn't like him do date one of my sisters but I am sure that wouldn't happen anyway..
I met a great lady, it just was not meant to be..