First she was worried that her airplane would crash because there weren't any airports.
Then she was worried that because..."Grandma is going to be on the bottom of the world"...she might fall off.
Her newest fear is that she is going to get burnt by the sun. (apparently she thinks that when the sun goes to bed in our neck of the woods and sets in the horizon it rests on the South Pole.
Poor Grandma, sounds like you are in for a pretty big adventure.