I'm sure you realize that if you choose the route I said would have been needed for me as a WAW, that she will turn to the OM.....out of sheer desparation, if nothing else. However, this places a great deal of pressure on him. She will discover just how much he is ready to take her in......or a ready-made family. At one time, you said he was long distance. After your transfer, is he any closer to where you are located?
I believe you need to think through all the scenarios you possibly can. For example, if she breaks down in sobbing tears and begs forgiveness and promises anything you want her to do to make the M work. Only problem, she did that the last time, didn't she?
What concerns me, and one reason I decided to give my opinion on this, is that her addiction to the A has drawn her back to OM again, and even if he rejects her, she could be a candidate for a serial cheater. That's why I think she needs something very tough.......very real......very shocking. You have the facts on your side. She doesn't know that you know. That is in your favor. Just don't let it slip how you know.
This is not a gimmick to get her back. It is very serious, and I believe you are looking at that with grave concern of the outcome, and most of all the effects on your children. I believe this is your last resort after the LRT. The only thing that is going to keep her there is either she cannot be trasferred where OM lives, finances, or being separated from the girls.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!