You need to set a boundary on that for sure. Her doing it is bad enough; you do not have to hear about it. Living through my H's A was horrifying, and in my case it went on for a long time. I think it's over but I don't know if it is or if there are others. I get the sense there is no one anymore but it has been five years since BD. I think my boundary on that front helped me and helped him face the A on his own without any pressure from me. I think it is perfectly fine to tell her that out of respect for your marriage, you cannot discuss anything she chooses to do outside of the marriage. Tell her that you respect her choice to leave the marriage and that you will not listen to any details and that you do not want to know where she is going or what she is doing unless it is relevant to your kids. With my H, whenever he tried to say anything about it, I would just say, "That's between you and God," or "I have nothing to do with that. That's between you and God." It was so clear that I did not want to hear about it that he learned quite quickly never to bring it up though there were some very dark periods when he was texting OW in front of me, said some horrifying things about her/me, etc. But generally I never had to endure more than a few minutes of it, and rarely, because of the boundary I established and stuck to. I had trouble with boundaries in other areas, but writing this now I realize that I did very well with that boundary, which makes me feel a tiny bit good!
Please know that we all understand the agony you are feeling. It is a deep wound. Try to remember that it's kind of like any wound caused by someone else (e.g., getting kicked during a soccer game, getting a broken arm when someone rear-ends you) -- you didn't cause it. It happened to you and it wasn't your fault. The wound is going to hurt. A lot. For a long time. And when you have dark thoughts, like the thought that you can't take it anymore or the thought that you aren't worthy or that you aren't lovable or that the despair is too painful,just remember that those thoughts are like the dull ache you get from a broken arm. It's not a new wound each time, it's the same one you already have. A priest told me that once, and somehow it really helped me to deal with the pain and look at it from a distance.
I believe I will see the bounty of the Lord in the land of the living. Wait for the Lord with courage. Be stouthearted, and wait for the Lord.