It is often hard to get someone like that to see her as others see her. I thought everyone had the inner turmoil going on that I did, and to the same overwhelming and unmanageable degree. Had no clue how fear ruled my life. I'm still learning. Someone saved me by steadily and calmly pointing out how my perceptions were different from the reality of the situation or the person.

Calmly hold on to your own truths. Question her often with a calm curiouslity about where her ideas are coming from and how they differ from reality; that there are her internal experiences only, not what everyone experiences. Keep letting her know therapy is a place she can get relief from her chaotic and frightening internal world.

Do what you have to for yourself. Spend as little time there or around her as possible. Take care of you first. My mother was borderline also and my greatest relief came when she moved 1000 miles away. Now I am in therapy and I see now that it would have been just what I needed when I was trying to deal with her. Therapy would give you a place to vent and help you deal with this too.