Talk about separation agreement, talking about moving day...mention boxes if needed. I am sure at some point she will try to talk about why she is doing this and how hurt she is etc. I will just tell her that I understand why she is doing what she is doing, tell her I support her, and if she is happier this way then that is what matters.
How about...
That you are trying to understand what she is going through...
Because, in reality, you really don't understand...
It's like if I told you that there was a shidtload of water in the ocean, you would agree, yet neither of us knows exactly how much water is in the ocean....
The depths of her are still unknown to her, how could you possibly know....
???
On boundaries....
I want you to also understand that boundaries are good for you. Setting them lets another person know what you are willing to tolerate, and what you aren't willing to tolerate.
However...
Pick your battles wisely. Just because you can, doesn't always mean that you should...
Give yourself time, understand the need, or lack of...
And ask yourself if that is really the hill that you are willing to die on....