Do you really think that people see a therapist because they aren’t getting something in their marriage? This is a very unusual and somewhat troublesome notion of therapy.

I also wonder what kind of severe mental illness does she have that enables her to do nothing for the family and allows her to act in anger and rage and people should put up with it. What does she have that she can’t control her words and behaviors? If her illness is so severe that she is unable to properly function (psychosis?) it could be at least somewhat and often fully controlled by proper combination of medications. Is she not on meds?