MC is not the goal, and you have seen where it has backfired at times. It is an opportunity, though. W probably believes she knows you and that you'll never change. This is a chance to challenge this. What does she expect from you in C? Probably that you will recruit CR to talk her into returning to M. If you give her what she expects, esp if it's negative, she's more confident she can walk away.
My suggestion, if she has agreed to go, is to begin with something she does not expect, like "I'm here to learn to be a better listener (or partner or communicator or parent - whatever you would genuinely like to improve about yourself)." It switches the whole dynamics from adversary to partnership - you've just asked for her (and CR's) help in becoming a better you! That can be very attractive and give her a vested interest in the outcome.
Something to consider, my friend.
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