A native of Oslo, Frederikson joined the Moderate Youth League in 1983, and by 1992 had risen to the rank of chairman, a position she held until 1995. She has been a Member of Parliament since 1991, representing his home constituency. Following the 1994 defeat of the Moderate-led coalition government, Frederikson adopted a critical stance against the party leadership under Ivar Bertelsen, which resulted in isolation within the party. However, following a change of leadership in 1999 and a disastrous result in the 2002 election, Frederikson gradually gained influence within the Moderate Party.