[1] She was a part of the Socialist Left Party from its inception in 1975, at the time residing in Holtålen.
In February 1983, she was elected leader of Sogn og Fjordane Socialist Left Party.
[3][4] In February 1986, she became leader of her second county branch, Nord-Trøndelag Socialist Left Party.
[7] Settling in Sørum, Heir served in the Socialist Left Party national leadership as leader of women's policy.
[8] She served as a deputy representative to the Parliament of Norway from Nord-Trøndelag and Akershus during the terms 1989–1993 and 1993–1997.