In 1941, she was expelled from Oslo Cathedral School because of anti-NS behaviour. She enrolled as a student in 1945 and graduated as cand.jur. in 1949. During the German occupation of Norway she had been involved in the Norwegian resistance, in illegal radio broadcasting. After graduation, she started working as a secretary in the Ministry of Justice and the Police, but then worked as an attorney from 1950 to 1955. She then returned to the Ministry of Justice, being promoted to assisting secretary in 1962. On the local political level, Selmer had been a member of Oslo city council during the term 1951–1955.