How can I help my mother deal with believing that her parents are still alive?
It is not unusual for people with Alzheimer's disease to want to call their parents believing that they are still alive. If telling them "the truth" does not work I use the "fix the problem" approach. Either give her the phone to 'talk" to them or tell her they are on vacation and she can record a message in a tape recorder to send to them. Then whenever she becomes upset and wants to talk to them you can have her record more messages. Validate her feelings by telling her that you know how much she misses them and encourage her to talk to you about them. Remember "joining in their journey, their reality, helps them LIVE a happier life.