Hm, I think it's mostly plot device as you said, but keep in mind that Japan has tremendous amounts of natural disasters, so fearing it can easily be explained by upbringing/childhood trauma/experience imo.
@KairenX
It's not about busy, it's about what she is busy with: Embrodiery. And she sells it to a shop. In short, for Nobles this is outrageous in the novel. Because it's beneath a noble to make a living off embrodiery.