Janet Frame endured eight years as a mental patient before she went on to become the poet laureate of New Zealand. She was misdiagnosed. While she was incarcerated she underwent electro-convulsive therapy without anesthesia and was lined up for a lobotomy until her doctor learned that she had won a prestigious literary prize and took her off the list. This movie is the story of three periods in her life. Her time in a mental hospital is the second.
I would guess that social anxiety and, perhaps, depression were the demons that afflicted Frame. She would hide in corners. She failed at her work as a teacher. When two of her sisters died, she crashed into a frozen despair.
If Angel at My Table is accurate, Frame was most certainly not schizophrenic. An early scene in the second part of the film shows her riding to the hospital in a car with two women who are severely impaired by their illnesses. She stands out as unafflicted by whatever is troubling her fellow passengers. Things were done to her while she was in the hospital just because they were the latest treatment. Her mother desperately signed the papers for the lobotomy: if Frame had been trapped in a mindless system, we would have lost a great author. Fortunately, a doctor noticed in time and helped her win her release.