She was the mistress of the Belgian poet Maurice Maeterlinck, who wrote the play Pelléas et Mélisande. Maeterlinck tried to secure the world premiere role of Debussy’s operatic Mélisande for Leblanc, but Mary Garden ultimately won the role, which she performed to great success. According to Garden’s autobiography, Debussy had Leblanc sing an act of Pelléas et Mélisande before a jury of musicians. The overwhelming results of that audition strengthened Debussy’s support for Garden.

Leblanc had a light voice of no special distinction. However, in 1903, she recorded an excerpt from Massenet’s Sapho. Its historic value lies not so much in Leblanc’s contribution but in the fact that it is a rare recording of Massenet himself accompanying the singer.

Critic Edmond Stoullig reviewed her 1898 performance as Sapho at the Opéra-Comique, describing it as “quite different from that of her predecessor [Calvé], which earned her personal success as an actress, singer, and woman.”