Janny has a strong reputation in local government, both in the Netherlands and internationally. She was a council member in the city of Leeuwarden, mayor of various municipalities and governor of the province of Drenthe. In 2011, she became a member of the Senate of the Netherlands. As Vice-President of the Platform for Municipal Peace, she established contacts with Eastern European cities in the early 1990s and developed a close relationship with the city of Srebrenica after the conflict in Bosnia-Herzegovina. She has been a member of the International Advisory Committee on international affairs of the Association of Dutch Municipalities and a deputy member of the European Committee of the Regions.