 The daughter of a civil servant, Horn was educated as a dressmaker and worked at Erfurt.In 1925, together with Marlene Dietrich, she worked as an extra in the German film "Madame Wants No Children", and later she was seen in a musical review by director Alexander Korda.She made her great breakthrough in 1926, when she replaced Lillian Gish as "Gretchen" in F. W. Murnau's UFA production of "Faust".