She'll reiterate all of the things she already said, "I don't want to be with you anymore, this isn't what I want, I don't love you and I cannot change that - and I don't want to try".
Agree with her. "I can't believe I have been trying to hold onto this. I hear you, I think it is best for me to be in a marriage with a woman who loves me. I understand how you can feel that way and I wont stand in your way of leaving."
There is a better option: Listen. Really get to understand her. DO NOT agree with her, but don't argue with her. There's a difference. (What you resist persists.)
Validating is not agreeing. It is letting her know her point of view really matters to you. You want to understand her side of things, and even more for a woman--her feelings. You want to understand how your actions or lack of actions have impacted her.
