My elderly father passed last year and my elderly mother keeps saying she wants to be with him. Some days are good and other times she says I shouldn't be here, I want to be with him. I reassure her that she is fine and it is not her time to go yet, so lets enjoy our time together and when God decides he wants you with him, only then will you be with Dad. What else can I do?
If not, you r doing what you can at this point. If she does have D, then her reasoning has gone and no amount of trying to explain and reason with her will work. Just I know Mom and a hug.