She began her career with the European Parliament as a member of the Green Left and then obtained her PhD with a thesis on European political representation, at the University of Amsterdam. In 2012, Buitenweg became a member of the Human Rights Board. Five years later, she returned to politics, as vice party leader and justice and security spokesperson in the Lower House. Since 2021, she has worked for the Council of State. Women's rights run as a thread through Buitenweg's activities. As a member of parliament, she campaigned for a better approach to stalking, sexual crimes and marital imprisonment. She has also been chair of the Clara Wichmann trial fund and ambassador of the 'My life, my choice, my body' campaign.