It's hard to know what she may think while she's packing, however, if you are there, I think she will go as fast as she can in order to avoid anything from you. I think if she knew you would be gone and she had all the time she needed, she would go slower, and therefore, good memories would stand a better chance.
If you packed for her, she would go through everything to make sure it was there. Don't be surprised when you get home and see a lot more gone than you expected. And, that would be the only reason I'd even suggest staying, was if you thought she'd take more than she should. I have seen some who literally dug up the rose bushes in the yard!
A real 180 would be to text her and tell her that you'll be gone and won't be home until late. So she'll have all the time she needs. I think she would be shocked, b/c she's expecting you to put up resistance. Like I said before, there is a reason she's taking daddy with her.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!