There she gathered much political experience, notably as an intern at the Quebec Government House in Mexico City and as parliamentary assistant to French politician Philippe Séguin.
In 2004, she won the Parti Québécois candidacy for the coming by-election in her native riding, Laurier-Dorion, and began a campaign of outspoken left-wing and sovereigntist politics (opposing the Charest government).
Coming at a time when the Charest government was low in opinion polls, her victory in the Laurier-Dorion was described as historic for reasons other than Lefebvre's relative youth.
In June 2005, after answering her question in the National Assembly about a possible conflict of interest involving his spouse, Premier Jean Charest mumbled "hostie de chienne", an insult which would roughly translate in English as "fucking bitch".
Lefebvre was recruited by Vision Montréal as a high-profile candidate for Montreal City Council in November 2009, in the district of Villeray in the borough of Villeray–Saint-Michel–Parc-Extension.
[4] Lefebvre announced in August 2017 that she would join the mayor's Équipe Denis Coderre pour Montréal for the November 2017 municipal elections.