You said she feels she has no choice. I do think you are right. But, make her see that she does have a CHOICE. She is choosing to not try anymore.
You are right that things could totally have been different had my H known about the OM sooner. In fact he said he would have kicked into action if I had told him that I was even considering it. I always try to think about what I would have done if.....that's how I try to help you when I post to you.
Sounds like you have a good plan. Just make sure that you don't give her everything. DOn't make it so you and her still have a R and that fulfills her completely because she will still get what she needs from you, and also from the OM. I know you want to keep the R, but that's what I worry about.