Hehn was born in Stuttgart, Baden-Württemberg, Germany on 13 February 1913. She was a Swabian. She later married, and gave birth to her daughter aged 25.

Hehn lived alone in her apartment until she was 105, when she moved into a Stuttgart nursing home. On her 108th birthday in 2021, she couldn’t meet with her family; they sang to her from the gardens. She claimed the secret to her longevity was, “I can do without.” She never smoked nor drank alcohol, but went out for walks regularly throughout her life.

In December 2021, Hehn contracted COVID-19. She suffered a high fever, aching limbs, and loss of appetite. Her grandson, wearing a protective suit, would help her eat. She isolated for 10 days, and later fully recovered, and went on to celebrate her 109th birthday by going out for a meal with her family.

Hehn died on 24 February 2023 at the age of 110 years, 11 days. She was survived by her daughter, as well as several grandchildren and great-grandchildren.