I, for one, applaud you. So many men in your shoes hear what your W told you and assume she means she's back in the M. But that is not necessarily so......and I believe you are staying pretty calm about it, so far.
To be blunt, she was basically telling you that her first option (or plan A) fell through and now she will have to go to plan B. Does that mean "you" are plan B or a divorce is plan B........or find another man.
I guess I am cold hearted, but I would have found it hard to show any empathy toward her and probably would not have validated, but you handled it well. When she tells you this type of information (or update in her drama) and leave it with open ends.......a out all I would know to say is, "I see". Continue using your poker face and voice. I mean, what was she expecting from you, when she called?
I loved the way you talked to OM! It was perfect! (Have you been mentored by Starsky, b/c it sure sounded like something he would have said.).
I don't have to tell you that this is a very critical time. The way you deal within the next several days could turn things one way or the other. I don't think I would ask her any questions about what she plans to do now. Certainly no talk about her & OM (until something is mentioned about reconciliation). I think you are correct in acting as if nothing has changed for you, and proceed about checking with her about an appointment with mediator.
Her fantasy castle was shattered yesterday for plans with OM. Doesn't mean it's over for them, but she's angry at him. While she is good and mad at him for not leaving his GF, I think is a perfect time for her to see you will not settle for left-overs. How far you want to go with it is up to you. But my point is that any chance of becoming a serial cheater or rekindling her A with this OM needs to come to a screeching halt, and the best time for that to happen is now. She will be watching to see what you are going to do.
If the A ends, She will still have to go through the withdrawal, etc., but one day at a time, right now.
I hope Starsky will come back and shed some light on this, b/c I think he had to go as far as to file for D in his stitch-- before the M was saved. I do not have personal experience with mediators, divorce lawyers, etc. I have read from others that they have gone right up to the court date and then the WAW would back down, however, there are never any guarantees and it can't be used as a bluff (in case it sounds as if I am suggesting you call her bluff). I just believe this time frame you are in at this time is critical.......whatever you decide to do.
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!