I need advice

So this girl was cheating on her fiancé and my husbands friend and his fiancé screen shotted everything and send it to that girls fiancé. (He's in navy school right now) well he went back to her and is telling the friend that he wouldn't and they're just talking and the fiancé is telling the girl that her fiancé better mind her own business and it's just a big mess. Were they in the wrong for being honest? Should the girl be mad at them and threaten the fiancé?