Complex sentence: She worked at the County Middlesex War Hospital, St. Albans, England, then at the Anglo-Belgian Base Clearing Military Hospital at Étaples in France, where she was the only Australian woman doctor until 1917, and was later promoted to the rank of Captain.
Split into simpler sentences: She worked at the County Middlesex War Hospital, St. Albans, England. She then at the Anglo-Belgian Base Clearing Military Hospital at Étaples in France, where she was the only Australian woman doctor until 1917, and was later promoted to the rank of Captain.