The daughter of Charles-Eugène Lavallée and Marie-Anne Lemieux, she was born Madeleine Lavallée in Montreal and was educated at the Collège Viauville de Montréal and the Collège Jésus-Marie de Saint-Barthélémy. From 1947 to 1950, she worked in the office of the newspaper "La Presse" in Montreal. Bleau founded the parent teacher association for the Bois-des-Filion school board and served as its president from 1967 to 1970. From 1974 to 1977, she served on the municipal council for Bois-des-Filion. She was secretary for the No committee in the 1980 Quebec referendum. From 1981 to 1985, she was president of the executive for the Liberal Party in Groulx.