As Dr Kansal has kindly said, yes paranoid schizophrenia
is ONE OF THE DIAGNOSES that she could be having
But there are many other diagnoses like depression/mania with psychosis
(particularly since she has these in attacks/epsiodic form) or delusional disorder
since she is elderly in age, schizoaffective disorder
since you describe both depression as well as paranoid symptoms etc.
I think the first thing to do is to go back to your psychiatrist
and find out what problem she has, then ask him/her lots of questions about managing her etc and her future i.e prognosis i.e weather she can be cured or she will have residual symptoms or if she is treatment resistant etc
NO ONE ELSE CAN SAY, WITHOUT EVEN SEEING A PATIENT, that she can be 100% treated.
Hope you are not having headaches with our turf wars but these are inevitable and are good for patients when done with respect.