With the return of democracy, Hertz participated in various government institutions. A member of the United Nations Observer Mission in El Salvador (ONUSAL), she was responsible for verifying that country's peace agreements. She was human rights advisor and legal director of the Ministry of Foreign Affairs from 1994 to 1998 – a position she resigned on 31 October of that year, when the Concertación government decided to take on the defense of Pinochet, who had been arrested in London on 16 October. She joined the Chilean delegation to the Rome Conference in 1997, which approved the Statute of the International Criminal Court. She was Chile's attaché to international organizations based in Geneva in 2003, a lawyer of the Ministry of the Interior's Human Rights Program from 2004 to 2006, ambassador to Hungary from 2006 to 2009, and in the latter year was appointed human rights director of the Ministry of Foreign Affairs.