Cactus Flower (1969)

Distraught when her middle-aged lover breaks a date with her, 21-year-old Toni Simmons attempts suicide. Impressed by her action, her lover, dentist Julian Winston reconsiders marrying Toni, but he worries about her insistence on honesty. Having fabricated a wife and three children, Julian readily accepts when his devoted nurse, Stephanie, who has secretly loved Julian for years, offers to act as his wife and demand a divorce.