Protecting myself and my family but still allowing my son to see his grandmother

[cad2009]

My mother has BPD possibly NPD. She vacillates between being loving to angry, cruel and even violent.  I thought that she as doing well but then on a gorilla weekend she became unstable, aggressive violent and then ultimately a weak sobbing victum.  It's been nearly a year and I have had limited contact with her.  I've been in therapy but I am only realizing now after she started calling again, acting like nothing happened that I may be suffering from PTSD.  I have found myself feeling irrationally feaurful of h showing up at my house ( she does not love on the same state) unexpectedly.  I a really afraid of her and though I feel sad for her, but mostly I don't want anything to do with her. I have discussed this with my sister, who has also been attacked by my mother, (something I've only recently discovered).

I just don't know what to do especially since I e just discovered that my mother has some health concerns that could be serious.