I do not want to attack Davina, nor do I want to attack Sean.
I think they each had habits the other did not like.
They like privacy/and probably have housekeeping and schedules the other was not one bit compatible with.
Not just leaving the toilet seat up.
both probably were used to showering at a certain time, watching tv at certain times,being on computer, eating,cooking, doing laundry etc.
It all boiled down to independent living, and maybe freedom is more up their ally than somebody you have to ask permission and everything to do what you want
when you want.
That is what I got from the little bit we saw of it all.