She should walk away and say nothing. It's not her responsibility. 52%
She should give the guy a chance to fess up to his girlfriend first, but warn him: If you don't tell her, I will. 24%
She should send the woman an anonymous note, email, or text. Because everyone knows what happens to the messenger. 16%
She should tell the woman in person or on the phone so she's more likely to believe her. 8%
