This sealed Stephen as untrustworthy to have a relationship with. It was one thing to be tempted with an effectively absentee girlfriend, but going behind his best friends back that was not good at all. If you can betray someone so close to you, not once, but twice then this suggests a pattern - one which will be repeated. Connor on the other hand had shown remarkable loyalty to his friends. He had temporarily lost his job because of that loyalty, but he would never betray a friend. Abby never asked herself "Why wasn't her heart breaking over this nasty revelation?"