Grace Livingston Hill 
Miranda 

No one ever would have guessed that one of the richest men in town wanted to marry Miranda—or why she had turned him down. But Miranda was faithful to another. And she relied on that faithfulness for the strength to clear the name of her secret love… and for the endurance to survive the hardship and danger of the Oregon wilderness until the day she could be in the arms of the man who had always held her heart.