I had the same happen with my mother.Would like to avoid something like this before it happens, but it is getting there.
Family are all trying very hard between the other crisis.
But currently everyone is evil.
She shut everyone out - would not allow me in the house when I went to visit her.
Would answer the phone but would then put down straight away.
Everyone was against her - she was convinced my wife was planning to kill her.
With help of friend I got her assessed by doctor who concluded she was a danger to herself and others (this is after she tried to run someone over with her car).
Due to her volatile and extremely violent nature ended up having to call SAPS to go to her house / breaking open the door and forcefully remove her (took 4 policemen to get her out - she bit one so badly he needed stiches).
After 3 days in hospital for observation she was transferred to Falkenberg (mental hospital in CT) where she was for 8 months.
Even on meds she had to remain in facilities (that were kak expensive) - she was kicked out of 2 due to her violent behavior and ended up in a lock down dementia facility for a few years before she passed.
I ended up going through the high court to legally be appointed to be in charge of her person and finances (2 separate things you shared custody with a lawyer)
She was never completely diagnosed orher than the vascular dementia that developed later on but was treated for "personality disorder"
Personally I think she was paranoid/delusional with uncontrolled anger issues. Even heavy meds made no difference other than to sedate and make her "manageable".
On a side note - my wife was a clinical psychologist so she was able to give me a lot of insight and help me understand some people are just beyond help.
I hope that is not the case here but as has already been suggested get the Dr to make both the assessments and recommendations.