How do I answer to my Mother about my deceased Father?

My mother has recently been calling me asking about how my dad is doing. He has been dead for nearly six years. I can’t seem to get through to her that this has happened, even though she was there holding his hand as he passed. I am racing trying to find an adequate facility to place her as she has bad memory trouble and has taken to wandering about at night looking for him. But where she is (Chicago) memory wards are ludicrously expensive. Here in Ohio somewhat less so. She has called me several times about Dad and maybe I should be answering another way?