My two cents-- I would keep with the MC. What's the down side? She says she wants to do it. I think the biggest reason people recommend against it if both parties don't have the same goal in mind (a stronger M) is that it sets up false hope/expectations for the LBS. I think as long as you can keep your expectations in check, there isn't a down side to MC for you. You will have to know, though, that there is a decent chance she's pursuing this so that she can check the box of "we tried everything." (I guess I don't think that is the end of the world, anyway. If she wants to D, she'll D you, regardless... it just helps soothe her guilt. Though on the other side, you refusing MC also helps soothe her guilt, so you're kind of in a no-win situation.) Just keep a close eye on how you feel and your own boundaries. For instance, perhaps a boundary for you would be switching the conversation thread in MC from "how can we make this work" to "what would a D look like for us"-- this was a boundary for me generally, not talking with my H about his fantasy D scenarios.
Going on weekly dates with her-- again, what's the harm as long as you don't have any expectations? If you can't control your expectations, then I would avoid, or at least avoid some, like if you are really nervous or notice that you are starting to have expectations around an upcoming date. Just don't imagine that she's going to suddenly fall back in love with you through a few dates.
In/re parameters around her moving out-- she said she wants to and has figured it all out, right? Okay! I think here you go with the flow. As everyone above has said, you can't control what she does anyway. I would also think that her background has something to do with her direction here and maybe she is not a typical WW just looking for an excuse to chase the highs of her infatuation/AP. My understanding is that a structured separation where each party agrees not to date other people, to stay in MC, and to have weekly 1-1 time is a pretty standard approach when the emotions of one or both people are running so high that it makes working on the R when living together impossible. Again, to me this goes back to managing expectations. You want to stand for the M-- don't date. But don't expect her to hold to the same rules. She may, she may not and you have to be okay with that. She may use up all her free time texting with her previous friend or finding another one. (This, by the way, was why i refused to a structured separation with my H, who wanted to live in the basement for 3 months and then see where we were. To me, I knew there was zero chance he wouldn't be in touch with his AP during that time, and I had a hard boundary around him actually leaving-- that would have been it for me.) You need to do some hard thinking about what you are okay with and what you're not okay with. For instance, if you find out it was a physical A-- would that change things for you? If she says she isn't going to date and then does during this S, how will you feel?
In the end, this S may be the first step towards D and you'll never live under the same roof again-- but you are going to have to learn to be okay with that since there is nothing you can do. Her choices. You control you-- so my advice here would be work as hard as you can on detaching, keep up the GAL, and work on understanding that you're going to be okay no matter what happens. Releasing the pressure on her should help a lot. If she is parsing out everything you say to the degree you're indicating like with the comments regarding whether or not you were truly supportive of her moving out, you probably will benefit a lot by having some time apart from each other.
Hang in there. I think you are in pretty good shape, TBH.
Me (46) H (42) M:14 T:18, D9 & D11 4/19 - 12/19: series of escalating BDs 9/20 - present: R and piecing
