8, Your W wants to legitimize her A by getting your D's approval of her new R. If D meets OM and likes him then W will feel vindicated. It's all about W, no thought to D. Is there a way that you can approach W and put forward the idea that it would be better for D to wait a bit. D has had to digest alot recently and it seems like a far better idea to let her adapt to the current sitch without adding the OM dimension right now. You don't have to state any approval or disappoval of what W has done, only put out what you feel would be healthy for D's mental health right now cuz "I know you care most about D's adjustment, dear W". I know, how self centred can one be but that's the way it is right now. Good luck with it 8. Lastly, DON'T assume talking with W will be useless and rush to a lawyer, take the high road first!
