A Voice in the Wilderness by Grace Livingston Hill

Margaret Earle, an Eastern girl, thinking she has reached her destination in Arizona, where she is going to teach school, steps off the train at a lonely, desert water tank, and the train moves on, leaving her in the darkness and in a strange, forlorn land. But she steps off into a series of adventures and thrilling events which make entertaining reading indeed. After an unpleasant encounter with one man, she is rescued by another, young Lance Gardley, like herself an Easterner, and out of this meeting grows the romance of the story. Margaret's school and the strange religious life of the community make a splendid setting for this fresh, crisp, western tale.