Grace Livingston Hill 
The Beloved Stranger 

Only minutes before Sherrill is to marry Carter, the man of her dreams, she discovers him in the arms of another woman. When Sherrill finds that the other woman is desperately in love with Carter, she decides the wedding must go on—with the other woman as the bride!
Later, as Sherrill arrives at the church to watch the wedding that should have been hers, she stumbles out of the car—and falls into the arms of a passing stranger. When Sherrill looks up to apologize, she sees a tall, handsome man whose piercing eyes seem to see deep within her. Shaken and distressed, Sherrill lets the man help her into the church. He stays close beside her throughout the ceremony and is her encouragement and support through the rest of that painful day.
Soon he is no longer a stranger… and more than a friend.