Aunt Jane's Nieces on the Ranch by L. Frank Baum

Louise had been considerably puzzled to account for the presence of the strange girl in Uncle John's party. At first she did not know whether to receive Mildred Travers as an equal or a dependent. Not until the three nieces were seated together in Louise's own room, exchanging girlish confidences, was Mildred's status clearly defined to the young mother.

"You see," explained Patsy, "Uncle John was dreadfully worried over the baby. When you wrote of that terrible time the dear little one had with the colic, and how you were dependent on a Mexican girl who fed the innocent lamb some horrid hot stuff, Uncle declared it was a shame to imperil such a precious life, and that you must have a thoroughly competent nurse."