Fiancee kissed and groped by his online friend?

My fiancee has a friend with whom she chats online and also texts a lot. She has told me all about it. That guy had intentions of getting physical with her and once has forcible taken her toh his room n kissed n groped her for a while... My fiancee told me all about this and she says that she loves me.. She didn't respond to that guy's moves... Im totally confused about what to do... to whom should I confide in this matter ?