What should i say

My Great Grandma is a well known pastor in the city we live in and she has quite a bit of money and plenty of assets, furniture and cars. She has well over millions worth of things. The problem is we have a big family and she doesn’t have a will or anything. I feel as if it is important to have one to keep confusions down when she does pass. Whenever someone brings this up she gets upset and think we’re trying to kill her off or something. As I can see her health slowly declining as she’s getting older, I’m afraid of how the family will be once she’s gone. With all of the things she has I know there will be lots of disagreements. How can I politely get her to see this is something that needs to be done.