Hi Mom of 5, welcome to the group
you'll find many members just like you here today looking for support -- because BPD doesn't take a day off.
It makes sense what you're saying about BPD being the most difficult mental illness. The lack of insight, plus the way it impacts the closest relationships, is so painful to watch & experience.
What was the diagnosis process like for your D24? Does she seem to accept the diagnosis, or resist it? Is she in any treatment right now?
One of the biggest lessons I've learned from this site is that it takes some pretty unintuitive communication skills to have better relationships with pwBPD (persons with BPD). We have a great section of articles on parenting a child with BPD up top, under "Tips" (the dark green tool bar). That can be a helpful place to start learning about some of those new approaches.
When your D24 says things like "I wish my family loved me", do you respond to that?
-kells76