Women who agree to go to marriage counselling on the request of their husband, while actively taking steps towards separation and divorce, are not going with a view to save their marriage.
If she comes to you and says “I want to work on saving this, let’s go to counselling” - that’s a different story.
But in your case, she’s going to help cement her decision. She wants to get the counsellor to reinforce her decision to leave. And if the counsellor doesn’t give her what she wants, then she knows she can just stop going and tell her family and friends “I even tried marriage counseling, I exhausted all options.”
That’s why a wayward/walkaway spouse normally agrees to marriage counselling. It’s a win:win for them.
It’s also why veterans on this site caution people over forcing marriage counselling after a bomb drop.
Both of you should seek out IC, that’s far more likely to be successful.
