Your W was unable to tolerate 48 hours of Retro. She mocked the entire process from what you posted because she was writing things like a spoiled child would. She felt pressured being asked to go to Retro and said you forced her to go. How is inviting her back to the R any different?
Your C is not listening to you. If she is she is simply suggesting you do more of the same that did not work the first time.
Your W couldn't do 48 hours - she certainly was not going to do an entire R.
Going dark and detaching are for you - your W has to feel the natural consequences of her actions. Your C is suggesting you can control how your W feels or at the very least you should try. Being mindful is one thing - inviting her back in the R so you have "insurance" for a future conversation is something way different.
Closure does not come with one action or conversation. It is a process that takes years and a total shift in thinking and behavior patterns.
If your W has a fear of being alone that is her issue to own and work on. Your W certainly was not very thoughtful of your fear of being cheated on when she was cheating, was she?
Her being left alone by you is a fear only she can work on. It will only "count" when she realizes it on her own, works on it by herself and understands how SHE contributes to that problem.
When something seems like a "good idea" regarding your W, wait at least 48 hours before you even think about executing it. Your emotions control you way too much.
Your C and healing is not for the benefit of your W. It is for YOU. Odd a C would say otherwise.