She was elected to the Norwegian Parliament from Hedmark in 1961. From August to September 1963 she served as the Minister of Family and Consumer Affairs during the short-lived centre-right cabinet Lyng. During her stint as cabinet member her place in the Parliament was taken by Karstein Seland. Grønn-Hagen had previously served in the position of deputy representative during the term 1954–1957, but a year into this term she replaced the deceased Einar Frogner as a regular representative.
Grønn-Hagen was a member of Tynset municipality council from 1951 to 1959, and became deputy mayor in 1959–1960.
Notes
^Replaced Einar Frogner as permanent representative after his death on 10 July 1955.