I had the same thought as annsixty
Whilst it would be a good idea to chat to her about it nearer the time perhaps it would be better not to make too big a thing about it to her; you may pass on your anxieties without realising it.
Apart from knowing that Grandad is not very well and has gone to the hospital where the doctors and nurses will make him better there should not be a need to go into more depth.
Does she live with you and spend every day with Grandad?
Another welcoming into Soop's kitchen for those who care to share...