Complex sentence: Her mother died when she was 13 but it was only when she was 16 that she moved to Denmark where she lived in the Copenhagen home of the artist Thorald Læssøe, one of her father's best friends.
Split into simpler sentences: Her mother died when she was 13 but it was only when she was 16 that she moved to Denmark. She lived at the home of the artist Thorald Læssøe, one of her father's best friends.