Sounds like schizophrenia to me. Schizophrenia is a state of severe distortions of reality often with hallucinations. There is a field of specialization called orthomolecular medicine which considers nutritional issues/defects as the basis for all mental illness, including schizophrenia.
Here are some resources related to nutritional approaches to schizophrenia.
Dr. Carl C. Pfeiffer was considered a pioneer in nutritional medicine and schizophrenia. He wrote a book called Mental Illness and Schizophrenia in 1987. I have not read it, but I have read Mental Illness and Nutrition which was quite interesting. Mental Illness and Schizophrenia is currently not in stock on Amazon which surprises me because it was listed a few weeks ago. The Pfeiffer Treatment Center in Illinois (http://www.hriptc.org/) specializes in nutritional investigation and treatment of schizophrenia, and other disorders.
Much as you might want to help, you may find it extremely frustrating and very sad. There are two members of my extended family who suffer with lesser degrees than the one you are describing. With their altered state of reality, they can be irrational.