Why does Dedè warn Minerva that ,"you're exposing yourself to an accident by going down all together"?

Dede becomes nervous about all of her sisters traveling together to visit their husbands, and her warnings serve as foreshadowing for their deaths. When they laugh at her warnings and she gets upset, Minerva says, "Come on, Dede. Think how sorry you'd be if something should happen to us and you didn't say goodbye." But before they leave, she cries out her real fear: "I don't want to have to live without you." The reader knows that is her fate exactly: to live after her sisters die as martyrs, and thus to tell their story.