I would ask if you dug deeper, wouldn't you see some of the negative signs in their character were always there? And perhaps just magnified and more visible because of the A? In my case, I had always told her she had a "princess mentality" and a sense of entitlement. She didn't like those labels, but they were accurate. Selfishness, problems telling the truth, a sense of entitlement, all charcter flaws of a cheater.
H:54 W:46 D:11 D:21 M:12 BD:1/15 In-house Separation 2/15 DB started 7/15, W sees consistency 9/15 Dropping the rope and having her leave 2/16, moves 5/16 Reconciliation 1/17 Obviously still struggling