It's very common that one partner thinks the marriage was fine, in fact, just like any other person's marriage with its normal ups and downs, but that overall it was good, and it may very well have been just like that in the eyes of most any observer, while their partner thinks quite otherwise but doesn't say so. People don't just wake up one day and decide to have an affair, there's typically some period of time where grave dissatisfaction has set in and gotten to the point where they became vulnerable.
People don't simply "fall" into sin, scripture makes clear that people are enticed by their desires, and dwelling on those desires leads them to act on them (James 1:14, 15).
What I suggested to Hopefloats was to achieve a more realistic view of who her H was and is, flaws and all. He had been engaged in an affair for several years. As such, he misled her, deceived her, lived a duplicitous life all that time. He abused their relationship. This was him, not a separate act during a weak moment.
