I am so sorry you are dealing with this unbelievably triggering stuff. Do you have any old benzo prn's left over, maybe?
I do not. So, when I get anxious, I can only breathe my way out of it. So, practice your Thich Nhat Hanh or whatever other kind of breathing you prefer. It really, really can help!!!!
I don't have any real experience with this. My father probably has a little dementia, but he is still high-functioning, relatively speaking. I found this link for a few sites you might want to check out maybe. Maybe they can help you out with some ideas.
Support Groups for Caregivers & Persons with Dementia / Alzheimer’s.
In the meantime, do something about her phone calling access situation, so she cannot keep torturing you.
I hope this gets better and soon, Blanche!!!!!!