How does she feel about moving out? I mean, in general, does she talk about wanting to move out?
I wonder if the recent rounds of hospitalization are connected to the pressure she feels coming from her "adult" age to successfully become an adult. Ending up in a hospital due to extreme behavior seems more like she's (unconsciously) seeking somewhere to actively avoid responsibilities. Not that it's purely her fault, just that the emotional pressures to care for herself overwhelms her ability to manage the volatility she has going on with her emotions.
My SD23 was described by her psychiatrist and therapist as chronically suicidal and knowing that someone you love is wired that way can bring you to your knees.
Have you heard of Marsha Linehan's memoir about building a life experienced as worth living? Linehan is herself BPD and was institutionalized for two years based on her BPD symptoms. Then she went on to develop DBT to help those who were chronically suicidal.
For reasons I can't articulate, reading her book helped me get over my fear of SD23 committing suicide. Or helped me put it in perspective, if that makes sense. That wasn't necessarily the point of the book, I don't think, but reading Linehan's story and how she learned to interact with suicidal patients (acceptance plus change) made me realize what I can and cannot do when it comes to SD23. It's not just a complicated problem, it's one of the most complicated, most troubling mental illnesses that even experts have struggled to figure out.
Linehan describes suicide as a failure to assert one's
self. Asserting one's self is explained in more detail in the book. The ultimate assertion of self is becoming an adult and all that it entails, which people who have BPD really struggle with.
Do you have a safety plan for D18? And how does she respond to having a BPD dx (assuming she has one)?
Where SD23 lives there is a DBT clinic that has different levels of care depending on how well someone is functioning. SD23 is not using those resources yet, but we know they are there just in case she experiences psychosis again. I believe it is level 2 that offers twice weekly group skills/ peer group, plus once weekly individual therapy and 24 hour coaching. It's the last part that SD23 really needs. She puts so much strain on family and friends that she wears people out. I think level 1 is inpatient. I can't remember level 3, but it might be the DBT skills group without the 24-hour coaching, I'm not sure.
I think there are a lot of solutions that can help and you're in the right place for support.