Sentence:  Caroline was that hard and unalterable fact which turned Martha's life, in spite of a pleasant and helpful <WSD>nursegirl</WSD>, into a routine which began at five sharp every morning when the light first showed, and ended at seven in the evening, when she went to bed. 
Meaning of the word marked with <WSD> tags:  A young woman employed to look after a baby or young child. (from 18th c.)