Not a huge point, but you are assuming that she is on this terrible path. This may be the best thing that has ever happened for her. She will die happy in the arms of this OM, or her subsequent partner.
I do not think this is an assumption at all. I have yet to see "happy" work out for a wayward spouse. I have dealt with 100's of couples in real life and read the stories of 1000's on the internet and have yet to see or hear of even one truly successful "happy" wayward journey. The statistics you often read on the internet forums sometimes is something like 3% of affair relationships result in marriages that survive 5 years. I'm not sure what study came up with that number and whether it's reliable. I think statistics in this area are impossible to truly nail down but I personally believe the 3% number is overstated. Further, I also surmise based upon observations and statements that very very few, if any, of such 2, 3, 5, 8 percent or whatever the true number is, are actually "happy".
Thus...it's not an assumption your wife is on a terrible and unhappy path. IMO, it is as close to a fact as one can get.
In fact, it's a big reason I try to push betrayed husband to fight for their wayward wives because SHE is drowning and destroying her life (as well as her family's). Instead of "if you love her let her go", I'm an advocate of "If you love her, TRY to save her". Your mileage may vary.
I think she APPEARS happy right now. In fact she is wearing a mask. I agree with GB that it is very unlikely to end well unless she figures out that her mask must be discarded and her real self must be dealt with.
As far as trying to "save her" not sure that we are capable of doing that, she has to FIX herself first.
