Hello qcarolr,
Sorry to hear that your dd is ill.
It appears that you are in a calm and centered place within yourself.

I can't know if your daughter is suffering from a diagnosable physical problem or not. I can however imagine how she could be stuck in a cycle of anxiety (panic).
When we are ill or even slightly debilitated we are very vulnerable, vulnerability we did not choose. Imagine being so vulnerable and in an unsafe environment with no resources. That is very scary and even traumatizing for a person with BPD. Her continuing symptoms may be from the trauma, from ailment, or brought on when she thinks about going back to that unsafe environment... .or any combo of the 3.
Do you remember when we talked about Mazlo's Hierarchy of Needs? How safety is necessary for one to be able to learn or progress up the ladder?
You have worked for years to find a place of safety for your dd. I understand that at the same time she was not willing to work along side you and she often destroyed her chances of having a safe place to live. This cycle of crisis and back to your home continues.
I don't know that there is an answer for how to disrupt this cycle. Maybe everyone is ok with the cycle continuing as it has for years.
Offering more prayers for wellness of DD and your continued strength.
lbj