Complex sentence: Her family divided its time between estates in Manhattan at 59th Street and Fifth Avenue, in Watertown, Connecticut, and in New Rochelle, New York, and she enjoyed the advantages of an upper-class lifestyle.
Split into simpler sentences: Her family divided its time between estates in New York at 59th Street and Fifth Avenue, in Watertown, Connecticut, and in New Rochelle, New York. She enjoyed the advantages of an upper-class lifestyle.