Complex sentence: On 9 February 1951, she became a naturalized citizen of the United States and in 1953, bought a seven-room apartment at 450 East 52nd Street in Manhattan, New York City, where she lived for the rest of her life.
Split into simpler sentences: On 9 February 1951, she became a naturalized citizen of the United States. In 1953, she bought a seven-room apartment at 450 East 52nd Street in Manhattan, New York City, where she lived for the rest of her life.