She was the daughter of the head teacher Einar Holger Hermansen and the seamstress Kaja Louise Hessing and she was the youngest of five children in the family.
[4][5] Hermansen also performed the roles of Gilda in Rigoletto, Norina in Don Pasquale, Olympia in Hoffmann's Adventures, Zerbinetta in Ariadne auf Naxos, Hilde Mack in Elegy for Young Lovers for the Royal Danish Theatre.
[1][2] In 1972, Hermansen began teaching singing at the Royal Danish Academy of Music and became an associate professor at the institution nine years later.
[2][3] She taught the likes of Tina Kiberg, Elsebeth Lund, Susse Lillesøe, Michael Melbye and Johan René Schmidt.
[3] Hermansen was described as not being "at all aristocratic, and with her good humour she was popular among her friends" and as having also contributed significantly "from her young years in the Danish Radio Girls' Choir to the great operetta roles with the Entertainment Orchestra and Grete Kolbe.