She played Dan Aykroyd's fiancée Penelope in the 1983 film Trading Places and had a supporting role in 1986's Manhunter.
Darnell is mother to three children, through her marriage to Physicist Sebastian White. They married in March 1984. In the early 90s, she retired from modeling and relocated to Larchmont, New York, where she met her current husband, James Edwin Darnell, Jr., Vincent Astor Professor Emeritus of Biology at Rockefeller University. She established a brand of women's dresses and opened Clotilde: The Dress Shop in Larchmont, NY.