At fifteen, Renié gave her first solo recital in Paris. In 1901, Renié completed the "Concerto in C minor" that she had begun composing while at the Conservatoire. On the advice of Dubois, she showed it to Camille Chevillard, who scheduled it for several concerts. She made strides in the world of women in music during these concerts as she received the first applause directed towards a women for both her performance and composition. These concerts established Renié, not only as a virtuoso, but as a composer, and helped establish the harp as a solo instrument, inspiring other composers such as Gabriel Pierné, Claude Debussy, and Maurice Ravel to write for harp. In 1903, she composed a substantial harp solo called "Légende", inspired by the poem "Les Elfes" by Leconte de Lisle. The same year, Renié presented eleven-year-old Marcel Grandjany to the Conservatoire, but Hasselmans denied him admittance; the next year, Grandjany was accepted as a student but not allowed to compete. This was due to the growing animosity that Hasselmans had for Renié as he realized his young female student was becoming greater than himself. At age thirteen, the first time he was permitted to enter the competition, Grandjany won the Premier Prix. Following his win, he enjoyed a long and successful career as he introduced the Renié method to the United States at the Juilliard School. In 1912, Hasselmans and Renié were reconciled; he announced that he was physically unable to teach at the Conservatoire and wanted her to take his position, although there were no female professors teaching advanced instrumental classes. However, the Conservatoire, as a governmental institution, required approval from the Ministry of Education for its appointments. During the French Third Republic, there was movement to separate church and state and Renié vocally supported the Catholic Church. Thus, she was not hired and Marcel Tournier was given the position. Instead, she started an international competition in 1914, the "Concours Renié,". This included a significant sum of money along with the prize, and had notable musicians on the jury over the years, including Ravel, Grandjany, and Pierné. During World War I, Renié survived by giving lessons, and gave charity concerts almost nightly, going to a fund called the "Petite Caisse des Artists" that gave immediately and anonymously to artists in need, even when a battle was being fought 90 kilometers from Paris and Big Bertha was bombarding the city.