I know a child (9 years old) who has been asking Mom & Dad about a 'big red fireball landing in the ocean and what would happen'. Also asking 'how do worlds end'. The child does not use the computer nor watch YouTube videos or the mainstream media.

OP question for you. Is your sister going through any personal (spiritual) changes at this time in her life? The reason I ask is because many people experience some type of apocalyptic dream while they are going through these changes and I'm wondering if that's the case with your sister.