My husband thinks I am two different people, and wonders where the "other" me went. Any advice?

My husband is functioning but confused. He is recovering from multiple problems (including cancer) and requires continued care. He knows there is me, his wife, and a nurse who comes daily, but - to him - there is also another woman who comes every day (me again). And when he talks to "me" or to "her" he asks "where is my wife today," or to me "when is she coming back" I have tried to handle this in a positive way . But today he said "you are avoiding my question - when is she coming back?" Help please!!