A criminal tried to rape his wife’s daughter
Question

                A worried sister asks what should be done as her mother's husband tried to rape her. He tried molesting her but was unable to succeed in having intercourse with her. Does this have any effect on the marriage contract between the man and her mother? Should she tell her sisters and her mother (even though the mother is unlikely to believe her)?
Praise be to Allah. 
          This girl has to tell her mother and her brothers so that they can put 
          a stop to this crime before it happens. The girl must not sit with him 
          in the place where he is sitting, rather she must keep away from him 
          even if he is her mahram. The mahram – even if he is a father or brother 
          – if there is no guarantee that he can be trusted (Allaah forbid), then 
          it is not permissible to be near him, rather the guardian should prevent 
          that from happening. If that can only be achieved by punishing or imprisoning 
          him, then so be it. Whatever the case, this girl has to take every precaution 
          to prevent this evil from happening.