Sounds like you had some meaningful conversation! I realize you want to avoid stress and conflict. Personally, when discussions of my BF were taking place there was some rightful discussion about a b c and if these were not deal breakers in moving.
As a person if I wasn't in a good place in my primary relationship and felt disconnected and disrespected. I would think many times about moving into a larger home where i might not be able to swing things by themselves if it didn't work. Seems like with your moral consious it would make it harder to leave or ask for her to find her own place.
I gucess the point is can you really make this move unless the relationship with Aeryn improves. With firm boundaries in place with all parties involved.