Complex sentence: In 1710, she lost her mother, who had withdrawn from her father's court to join the Carmelite Convent in Paris, and who had been living at the convent for over 30 years when she died.
Split into simpler sentences: In 1710, she lost her mother who had left her father's court to join the Carmelite Convent in Paris. She had been living at the convent for over 30 years when she died.