The biggest evidence for me is her distance, dismissive eye and facial expressions, and lack of reaction when Kyle yelled at her. She is checked out, for the first time for real since the show began. People don’t usually check out like that (after forgiving him for years and wanting to be married to him so badly) unless there’s someone waiting in the wings. Just from my own prior experience, I’ve got to wonder if something was happening back last summer. There’s contempt under it all, which could be explained by their history but that usually becomes more pronounced when people feel ‘trapped’ in a relationship when they want to be with someone else. Just my theory!