Hello Frida and welcome to the group

"Constant struggle" sounds accurate. It already isn't easy parenting teens and young adults. The more support you can have on your journey parenting a child with BPD, the better for everyone.
Did your D receive a diagnosis? If so, when did that happen, and is she accepting of it?
Is she in school or working right now? How is that going (if it is)?
This is a great place to connect with other parents and family members that want to be effective and nurturing, while taking care of themselves.
Let us know how you guys have been doing lately;
kells76