The Little Train Home by Sheila Newberry
After an unhappy experience in her first job, sixteen-year-old, Elinor Odell takes the little train home to her family one snowy Christmas eve. But she soon realizes that her idyllic childhood has come to an end and that everything is set to change. Elin applies for a position as governess and companion to the Lamberts, who treat her as one of the family. She grows up herself whilst caring for their children; making close friends, falling headlong in love with an older man and supporting her beloved sister Jenny, trapped in an unhappy marriage. But, when the Lamberts suffer a tragedy, it is up to Elin to hold them all together and selflessly postpone her own fulfillment. Will she ever find happiness?