Im with Rob. I did not tell my kids anything other than we were divorcing. She went and told them its because "she found out some things about herself and she was gay". She did so without me. She said all of the things she told you, "my new partner will have to like you, we will have dinner together and be best friends, blah blah blah. All done to get me/you to go along so they arent the bad guy. No ability to accept accountability at all. I hope your situation is different, but sounds identical. If you decide not to play along, be prepared for her to go full victim mode. Mine isnt really even gay I dont think, perhaps bi, but being bi would not enable her to escape accountability, so she tells people she is gay. Bottom line, she isnt a good person.
Wishing a different outcome for you my friend