I too think if it wasn't this OM it would be another. My W also had retroactive feelings. My W also had something similar happen 3 times before, but no where near the extent of this recent EA. The other 2 times ended very quickly, long before the "friendship" got out of hand or threatened our M. I think the type of person that looks elsewhere is just that type of person, and will look no matter what. Does your W look at herself as a source of her problems, or is she always blaming other people/circumstances? Mine is always looking externally--I think that's symptomatic of a spouse who cheats. So, bottom line for me is that this is simply part of their character and until the sin is crucified it will remain part of their character. There is nothing unique, special, or better about the OP.
