How Do You Tell A Parent Their Child May Be Lying To Them?

We have friends their daughter is in communications in college and got ger degree this summer. She has been an intern the past 2 yrs for a man and telling her parents she is staying with his family while there, found out he has been seperated for the last 2 yrs. Her parents are not aware of that and are excited he is offering to help her in her career?? Trying not to ramble.