I don't know what to say. My dad died suddenly, 26 years ago. It was a huge shock and it messed me up for the next 10 years. As I've gotten older I've grown to accept what happened. None of us can know when we will be called. I firmly believe that there is no suffering after death, only us who are left behind suffer. But be happy for your grandmother. She has moved on to a better place.
Hugs to you.