Complex sentence: Her mother, Zulma De Lacy Thomas, shared a mingled Huguenot and Catholic descent, and was the daughter of French refugees who fled from San Domingo during the insurrection of the slaves near the close of the 18th century.
Split into simpler sentences: Her mother, Zulma De Lacy Thomas, shared a mingled Huguenot and Catholic descent. Her maternal grandparents were natives of France, who fled to South Carolina from San Domingo at the time of the servile insurrection in that island, near the close of the 18th century.