Hi Superwoman1 and welcome to the parenting forum! I am so glad you found us and are here, but, oh my gosh, you have so much on your plate - I am so sorry for the circumstances that brought you to us.
I also have a BPD daughter, 21, so I can relate to the black and white thinking that you describe as well as the anxiety and depression. So caught up in her own emotional turmoil that you end up feeling like a punching bag... .Truly not fair when you should be putting your focus on your own health and recovery. I am so very sorry.
It is good that your daughter is in therapy. How is that going, does it seem to be helping? When you say that she hasn't been told that she has BPD, does this mean that she hasn't officially been diagnosed? When you feel up to it, Superwoman1, please tell us a little more about your situation and what you are dealing with. Are you and your husband on the same page, supportive of each other, when dealing with your daughter? Does she live with you?
In the meantime, I will point out the excellent tools and lessons on the right hand side of this page

They should help you begin to better communicate with your daughter as well as learn to better manage your own reactions to her extreme behaviours and words.
We look forward to hearing more from you, Superwoman1. You are among friends here - compassionate, caring folks who truly understand the heartache of dealing with a child with BPD behaviours. You are not alone.
MomMae