How best to explain the death of a loved one to someone with dementia?

With dementia I think it's best to spare the person the pain and/or grief over losing their loved one especially if they've already grieved. In telling your mom that her mom is dead your mom may react as if it's the first time she's learning this. She may feel shock and grief, confusion and depression. She might want to know everything that happened thus going through it all over again.

Telling your mom that her mom is unable to travel right now is the kindest thing you can tell her about her mom and it spares your mom from the grief and pain she would feel as if she were learning about her mom's death for the first time.