Hello Foreverhopeful2

Welcome to BPD Family. As
zachira said, you're taking the most important steps to help your daughter.
The fact your daughter (DD) is open to trying a new treatment plan is so great, odds of success are definitely increased with acceptance and a desire to learn ways to improve her life.
It really sounds like you and your family have been through a lot and being told your DD has traits of BPD can truly be devastating. I'm glad you have taken the advice of your therapist and sought out more support. Being part of the BPD Family has brought comfort and hope to me and so manyothers. I'm glad you're here.
I'm going to be honest and tell you, I have created very harmful patterns with her by trying to protect, "fix" and make it all better.
Many parents here, myself included, will tell you they have behaved similarly. It's natural to want to help our children, ease their suffering. When I was new here I remember being told, "You did the best you could with what you knew, and when you knew better, you did better."
We now have to change our complete mindset on how to respond to her threats, needs and behavior.
You're right about that, and it's only recently that I have surrendered to this realization. You're ahead of the ball and it's clear you are willing to do what it takes to support your DD.
I encourage you to keep posting, read and participate in other's threads, become part of the family.
Yes, there is hope at the end of the journey. It won't be quick and it will often be challenging. But we've got you.
How old is your daughter?