Sadly sometimes a person becomes a revert for the wrong reasons. Maybe, your friend did not truly revert but only rebeled against family and authority. If that is the case, then possibly your friend has discovered that coming to Islam is not an escape from authority, it is a true submission to the Highest Authority.
Maybe you need to speak gently with your friend and learn why he/she made the choice to wear the name of Muslim. Help your friend learn the true reasons for reverting and help guide your friend on the path of having truly reverted.