Welcome to BPDFamily, glad you found us - sorry it was necessary.
Obviously none of us can know what is or isn't the case in your home (or, often, in the mind of a loved one with BPD) - but if she seems to consistently want to remind you of her unwillingness to live there and you're just looking for a short-term solution to avoid something bad coming to fruition - consider "caving in" in some small way that will allow her to feel like she's achieved some victory that allows her to now begin the reality of healing (again, not necessarily great long-term advice since you're "giving in"; depends on circumstances only you know).
For example you could offer that having talked about her "concerns" you guys have decided to pay the $45/month for her to spend the first Friday of every month at the local roadside motel enjoying the cable tv and convincing herself she's independent :P But phrase it as a mental health vacation away from you two crazy old parents, of course. Or perhaps let her change which room in the house is her bedroom so she can "start fresh", or some other little token effort.
It won't do much in the long-term, but for whatever reason I was looking at your story as just needing a quick bandaid solution to help her acclimatize to life back from the hospital and not having an organ-rejection of her homelife in the meantime. I apologise if I'm off-base, busy night tonight...loved one with BPD myself, you know ;)