Hello Ozz7

Let me be the first to welcome you here.
I am so, so sorry you lost your daughter! I can only imagine how difficult that was for you... .well... .still is. To go through something like that and then know you have the added responsibility of getting her children, your grandchildren, through the loss and grieving process too is more than I can fathom.
From one grandmother to another... .a ((HUG) .
It is good that your granddaughter has been officially diagnosed. "It" has been given a name so you will be able to look for the "tools-of-the-trade", so to speak, on how to deal with her behaviours.
You certainly have come to the right place to vent, to learn, to get support. While all our stories are different, there is always someone who is walking down a similar path... .can truly say, "I know how you feel."
When the time is right for you, hope you can share more of your story. What lead up to your granddaughter being diagnosed with having BPD. What are her behaviours?
You mention that there are 2 granddaughters. How is this affecting the other one?
So, Ozz7, glad you found us and hope you will feel the same way. This is a very supportive community. There is no judging. We truly do learn from each other. It is oh so validating to know one is being heard.
Huat