Born in Saint-Jacques, Lucie was the daughter of Charles Morneault and Pélagie Thériaut. She studied at the Academy of Saint-Basile and Normal School in Fredericton before becoming a nun in 1916. She taught boys and girls and was the head-mistress of Sainte-Catherine boarding school. Sister Morneault had an excellent reputation as a Superior, but no equal to when it came to building. She had the Sanatorium of Saint-Basile and the Hôtel-Dieu of Edmundston constructed at the same time, both openings were in 1946. On top of that, she favoured the progress of College Maillet and encouraged the sisters to study. She had written under the crucifix in her classroom Jesus autem tacebat. Sister Morneault died on Good Friday of 1957.