I don't know where you get some of these ideas when you haven't read the book yet. You don't have to cut off family contact. In most cases it is best not to get M advice and/or interference from your friends and relatives.
I think you should meet your FIL for coffee, especially if you have had a good R with him. It is up to you if you want to answer any questions he may ask. And he may ask if you want the D. Tell him the truth. OTOH, he may not ask anything and just express his sorrow.
I'm not suggesting you get on FB and blab to the world about her A, but you aren't obligated to cover up the truth from immediate family members. She may not want people to know the real reason she wants a D. A lot of women prefer others not know they want another man, and may even expect the LBH to lie for her. After all, the truth isn't always pretty. But your W was the one who told you her dad wanted to meet with you......and she didn't coach you, right?
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!
