In 1939, Steinhoff became a cook, married and had one child. In 1944, because of the Nazi call for new guards, she joined the camp staff at Stutthof. On October 1, 1944, she became a Blockleiterin in Stutthof women's camp SK-III. There, she took part in selections of prisoners to be sent to the gas chambers. On October 31, 1944, she was promoted to SS-Oberaufseherin and was assigned to the Danzig-Holm subcamp. On December 1, 1944 she was reassigned to Bromberg-Ost female subcamp of Stutthof located in Bydgoszcz not far from Gdańsk. There on January 25, 1945, she received a medal for her loyalty and service to the Third Reich. She was devoted to her job in the camps and was known as a very ruthless overseer. Soon before the end of World War II, she fled the camp and went back home.