Loth,
Well, this is a tough one. I'm sorry to hear your family is going through this. We went through a very similar situation with Duckie when my grandmother died last spring. I was lucky that talk of death isn't taboo in our family, so she could talk to many people about what was happening. The first thing we did was make it perfectly clear that Grandma was seriously ill and wouldn't survive the illness without a miracle. We then talked about what her life would be if she did survive, how very small her world would be after being ravaged by sickness and stroke. We talked a lot about how much we all loved her and how it can be hard to let someone go. We talked about how much Grandma loved each and every one of us and how love doesn't change after someone dies. We made sure she could talk to our church Deacon & Priest when talking to family wasn't good enough. I dried her tears and held her tight, but Duckie got through it.
I'm sure your Missy will as well.
{{{Hugs}}}