Trained as a biology teacher, Simeonova worked as a senior ecologist for the city of Botevgrad on environmental issues before the democratic changes in Bulgaria. Simeonova later became the executive director of the Foundation for Ecological Education and Training (FEET), founded by the Bulgarian Green Party in 1991. Campaigning against the construction of nuclear power plants, in 1994 Simeonova organized the first public debate between the proponents and opponents of nuclear power. One of Simeonova's most successful and novel initiatives to date has been the creation of "Ecological Inspectorates" at the local level. Citizens call to report local environmental problems and get a swift, independent response from professionals. Sometimes Simeonova alone responds. Following her lead, municipalities have now organized their own "Eco-Inspectorates," or have provided funding to NGOs to start them. The original four inspectorate programs have grown to 25 and more are being planned.
Seeing the need for nationwide coordination amongst environmental NGOs, in 1993 Simeonova persuaded environmental groups in Bulgaria to come together in an association called the Green Parliament. She also has involved citizens of Bulgaria and Romania to address the problems of trans-boundary pollution. As vice president of the Bulgarian Green Party, in 1995 Simeonova organized a dialogue involving members of the Green Parties of Western and Eastern Europe. In 1996 Simeonova co-founded the Bulgarian Green Federation. Though not a lawyer herself, she has written municipal environmental regulations. In 1997 Simeonova helped establish the Green Justice Association, which works together with local authorities and NGOs to create new environmental legislation.