Brunner was a local councillor in Mogersdorf between 2002 and 2005, being elected to the local council as an independent member on the ÖVP list. She subsequently switched to the
Green Party and has represented them in the municipal council since 2008. In addition, Brunner has been the district party spokeswoman for the Greens in
Jennersdorf District since 2005. She is also a federal congress delegate for Burgenland and ran for the third place on the list in the 2005 provincial election in Burgenland. Brunner prevailed over the previous member of the National Council, Michaela Sburny, in drawing up the list for the 2008 National Council election and ran for the fifth place on the federal election proposal of the Greens. Brunner was sworn in as a member of the National Council on October 28, 2008, and as spokeswoman of the Green parliamentary club she took over the agendas of environmental, anti-nuclear and energy policy, as well as animal protection. In the legislative period until 2013, she was a member of the following committees: Standing Subcommittee on European Union Affairs, Subcommittee of the Committee on Agriculture and Forestry, Subcommittee of the Constitutional Committee, Committee on Agriculture and Forestry, Committee on Petitions and Citizens' Initiatives, Committee on Economy and Industry, Environment Committee, Transport Committee. Brunner has been involved with the citizens' initiative against the (S7) since 2003, and with the citizens' initiative against the
Heiligenkreuz waste incineration plant since 2006. == Private life ==