I had a gut feeling that would happen at some point. So far, you have not described anything in terms of her actions that smack of even the tiniest hint of remorse. She is still 100% wayward in her heart; 100% in infidelity.
I agree with the others above. She already knew you told the OBS when she asked her leading questions. She did it that way because protecting the A is still more important than being honest with you. As I said, her default for over a year is to lie, sneak, and cheat. That will remain her default for some time. She will not flip overnight. She is still three steps ahead of you in this game, because she is still being conniving and dishonest (including throwing a little pussy your way to keep you off balance), while you are being honest and loving. She will always be ahead of you until you understand and accept that.
Stated another way, you are a barrier between her and the good thing she craves. Her mind is working 110 mph to figure out ways around, over, or through you. When she looks at you, she doesn't see you. She sees an unwanted object in between her and her desired place.
The point of this site is to get yourself out of infidelity. You have been hanging around in infidelity, hoping without reason that she might "wake up" magically and everything will return to normal.
That is not going to happen. Here is your current reality: she loves the A, and what it gives her, more than she loves you and her marriage to you. Now that the POSOM and his OBS are divorcing, it is quite likely she is pining for a future with him. By the way, a successful future with him is almost totally unlikely, but in her daydreams, that is where she probably sees herself.
You have good advice above. Get a lawyer. Start the D process. This process takes like a year or so. There is plenty of time for her to start showing remorse, and you to stop the process, if it comes to that.
Also, there is the family messaging. I told you to get in front of that so you are the first message to family, before her. You've lost that opportunity now, at least with your MIL. Now, the first message the MIL has heard is the message from your WW, which doubtless is casting this as you being a distant, controlling asshole who drover poor WW into the arms of another man, and then a controlling meddling asshole who is trying to embarrass her publicly.
You're probably too late to be the first message to the FIL also, but since he is your boss and since you are a key employee there, your career probably hinges on your next conversation with him. I would strongly suggest the "man to man" conversation that I described a few posts above.
Friend, my overall advice to you is to stop being passive. It's not a surprise that you are being passive. Most of us posters here are former BH's. We were passive. I did the "pick me dance" big time in my circumstance. I was pathetic. On the day I moved out, when my WWGF was in our shared house with her new BF and I was giving her my key, I was crying and kissing her and telling her she would always have the place in my heart and the ability to come back whenever she wanted. I was a soppy mess.
Don't be me. In your case, your job and livelihood is at stake.
On a small point, you mentioned that when you spoke to OBS, you had a ton of detail, including hotel receipts. How did you acquire all of that detail.?
[This message edited by Butforthegrace at 9:33 AM, July 12th (Friday)]