Grace Livingston Hill 
According to the Pattern 

Miriam Winthrop is ready to fight fire with fire. Her marriage vows were made to be kept, not empty words that now were echoing from room to room in her lonely home. Her husband, Claude, has become infatuated with another woman. To win his heart back again, Miriam must become all that “the other woman” is and more—a woman of sophistication and beauty.