i would say, that your stepmother has
having a neurosis more likely than a
psychosis. I'm not a doctor, but I do
have psychic problems.
Also for neurotic people, it makes sense
to do a psycho therapy. These problems
are followings from the early youth.
According to alice miller, who wrote a lot
of very good books (the latest: 'eva's
awakening') different forms of violence
lead to different forms of neurotic or
even psychotic problems. These problems
your stepmother has are forms of anxiety
and paranoia.
Within his biography, john mcenroe, the
famous tennis player of the 80's is
writing, that he was having kind of
paranoia, when he was not even no.1
anymore. He was thinking every referee
was not being fair. This is paranoia, if
you think everyone is against you.
You should discuss with your dad and all
together with her these things and try to
convince doing a therapy.
By the way, I don't think neurosis or
psychosis should be called illnesses.
Many people have a problem, when the
speech comes up with illnesses. And it
also implies for many people, at least
here in germany, that it cannot be solved.
Mental illnesses are mental problems,
they can be solved, if people start with
the solution, but it takes usually
years.