Let her remain in your sponsorship as a kind justice until she progress in such a matter.Anyway you donot have any legal binding on her. Be kind to woman. You have to explain anything and everything to a woman by love and not by anger. Just think this: Your divorce would have taken place if you solved family issues among husband and wife only. I think here the Mother of girl is villain. She must have encouraged her that the mother will find better bridegroom if she takes a divorce.

This is not to blame anyone. There is a lesson in this story for everyone.