In your timeline you say that you tried MC and it was not effective, and she was still seeing OM at the same time. I think you should refuse to repeat the mistakes of the past, and that is one of them. I would insist on Retrouvaille. She says she wants to be your first choice and she wants you to be her first choice. Then she needs to act on that, and going to Retrouvaille with an open mind and a willing heart is proof of that. That is all anyone will ask of her at Retrouvaille, that she go there with an open mind and a willing heart. Under those conditions, Retrouvaille is many times more effective than MC. And, if she wants to continue with MC after, that is fine.