My sis was a Clinical Psychologist for 20ish years until she retired and when I asked her about mum she gave the paranoia as a definite diagnosis. I think she actually said schizophrenic paranoia.
I've often wondered myself whether it is hereditary, and have always felt there's a chance I'll go that way too and that i should watch myself for similar symptoms.
But is that
one of the symptoms?
Eta: my mum was also deaf, and because she couldn't hear us when we were talking as a family often thought we were talking about her. I'm sure that fed into the paranoia and made it loads worse.