Tell elderly (early signs of dementia) grandmother her son died, or keep it a secret?

Hello everyone, seeking any and all advice.

My grandmother is 87, a little frail but not too bad physically, and is suffering from early signs of dementia/Alzheimer's. Her youngest son (my uncle) is on life support from a sudden brain aneurysm. She lives in Hawaii with her daughter and me, while my uncle and the rest of the family are in Korea.

He has unfortunately suffered too much trauma and only has about a day or two until they will harvest his organs. My mom is incredibly distraught and wants to see him before they pull the plug...but her and the rest of the family have decided to hide this from my grandma. They all say that she will lose her mind and if she finds out, then we'll need to plan for two funerals instead. We have the means to travel there so money isn't a concern for this situation.

My grandma is a strong Christian with very strong faith, but she was raised in Korea with very stubborn ways. Her children are her life and I could see her going down a terrible path if she finds out. However, in my mind, she still deserves to know the truth. My family is still adamant that telling her would destroy the rest of her life. We even spoke to her pastor, who told us that we can't tell her. Same answer from all the other Korean Christians that we asked. When we asked local/American people, they were all shocked that we would even think about hiding this from her (which I suspect you will all agree with).

Idk what to do. We've all prayed and cried over this, and while it seems right to let her know so we don't rob her of her chance to see her son one last time, we're all so terrified that she'll abandon her faith and live the rest of her shortened life in agony. My mother said that my grandma believes that if your child dies before you do, then God is punishing you because you've done something terrible in your life. We all have so much to say about that, but my grandma is so stubborn that she would live the rest of her life blaming herself.

Appreciate your time and help with this. God bless you all.