In 1990, Petrus permanently moved to Saint Martin to work as a teacher.[3] She later became principal of Emile Larmonie primary school in Cul-de-Sac [fr], Saint Martin.[3] Petrus has served as a volunteer firefighter in the mid-2000s, after accompanying her son to his firefighting training in Guadeloupe.[3]
In the 2020 French Senate election, Petrus was nominated for the Senator of Saint Martin seat in the French Senator by the majority UD party.[3] Her opponents included incumbent Senator Guillaume Arnell of the RDSE group, who was seeking a second term.[4] The island's lone national senator is selected through an indirect election by the Grand Electors of Saint Martin, largely made up of members of the Territorial Council.[1][5] Petrus failed to secure a majority in the first round on 27 September 2020, receiving only 10 votes,[1][4] but won the second round with 68.2%.[1][5] Petrus won 15 votes in the second round, versus five votes for Marthe Ogoundele-Tessi, and two for outgoing Senator Guillaume Arnell.[5]