I know how sad
this is for you. Your mother seems to be suffering from the dementia
associated with Alzheimer
It strikes women more than men, and by age 78, could be well advanced, particularly if she is suffering from paranoid delusions, and from wild mood swings. Some of the symptoms include paranoia, hallucinations, illusions, and delusions.
There are some treatments that can alleviate the symptoms but it cannot be stopped, only perhaps slowed down.
I urge you to have her examined by her doctor or by a gerontologist, and she can get medicine that will be appropriate for her.
Because she does have paranoid thoughts she may resist treatment, but you must gently coax he, and perhaps do it under the guise of a checkup rather than to tell her something that she will not believe and fight against.
I am including below an article for your enlightenment.
I shall keep her, and your entire family in my prayers.
Elliott, MAE, LPCC, NCC, CCMHC