Lilar began her literary career as a journalist. She reported on Republican Spain for the newspaper "L'Indépendance belge" in 1931. She later became a playwright with "Le Burlador" (1946). It was an original reinterpretation of the myth of Don Juan. It was told from the female perspective. She wrote two more plays, "Tous les chemins mènent au ciel" (1947), a theological drama set in a 14th-century convent, and "Le Roi lépreux" (1951), a play about the Crusades.