So this guy was in a group discussion with his GF and her girl friends about their previous hookups? Why was he there and why did she think it was alright to discuss this in front of him? Gotta think he gave her the impression that this was fine, which was his big mistake. If true, he came to a sudden realization that he'd lost or never had her respect, but it sounds to me like she was following his lead and doing her version of repenting of her past.