Complex sentence: Then her Mother and Aunt start talking about the trouble they caused for each other when they were young, and Beezus learns that sisters may not always love each other, but once they're grown up, they can turn out to be quite nice after all.
Split into simpler sentences: Then her Mother and Aunt start talking about the trouble they caused for each other when they were young, and Beezus learns something surprising about sisters. They may not always love each other, but once they're grown up, they can turn out to be quite nice after all.