What your friend needs is to learn how to choose a nice person to have a relationship with,
People pretend a lot, so you can never really trust someone. Someone may appear nice and act nice, but not really nice.
I believe that everyone here who is married shares information with their wives or husbands, after all a marriage is about living life together sharing everything, right?
and I also was not referring to people who are married, but people in a relationship.