I have a secret that hurts people. And I miss my friend. What do I do?

Ok personally, id try to meet with the guy and tell him yourself...and tell him youve known and she kept telling you she was going to tell him and that you dont feel its fair to him to keep the secret...if you lose her over it then she wasnt a good friend to begin with and its her loss but atleast you would possibly be helping out a good guy....good luck