SMALL TALK: Would You Send a 'Hey Girly' Message?

The dreaded Hey Girly message. If you don't know what that is, it's the decision to message a poor girl to let her know her partner has been caught out doing the wrong thing (cheating, on a dating app, flirting with others, done something in his past, been particularly rude). To receive one is the worst but to have to send one is equally terrifying. Would you send it? How would you react? Would you be thankful?