Harel was born in Sainte-Thérèse-de-Blainville, Quebec. She graduated in 1977 from the Université de Montréal with a law degree and was admitted to the bar in 1978. She worked at the national secretariat, the Centre des services sociaux de Montréal and the Social Development Council of Metropolitan Montreal as a staff member. She has been a member of the Parti Québécois (PQ) since 1970 and was the president of the party in Montreal-Centre in the 1970s and the vice-president of the party province wide from 1979 to 1981.