Hi Karen,
Welcome to the group. I'm so sorry for what you are dealing with, but yet so happy for you that you are still able to have a relationship with your grandchildren.
So many grandparents on this site struggle with the same issues as what you are dealing with, and some have been completely cut out.
Even in my personal life I have two friends who were completely cut out of their grandkids lives. In one case the children grew up believing their grandmother was dead. Even though she lived in the same town. I thought she was a sweet and kind lady.
I feel like the communication tools on this site would be the most helpful ones for you to learn. I encourage you to read the ones under: Tools at the top. I hope that if you find a new way to communicate with your daughter it might be the thing that saves you from losing your grandchildren.
This is a difficult thing to learn, I am still struggling with it. It amazes me to recognize that the people on this site are so intelligent, so loving and skilled and yet find that the learning how to communicate with their BPD adult children part is the hardest thing they have ever had to figure out.
You can do this. Make it a priority. Learn and practice all you can. Stay with us, we learn from each other. And most of all - if things go downhill remember you tried.
Take good care,

R