She made her debut at the age of sixteen, at the Teatro di San Carlo in Naples, as Rosina in "The Barber of Seville", which would become her best-known role. Following her debut, de Hidalgo was quickly engaged for Paris, where she sang Rosina opposite Feodor Chaliapin as Don Basilio. Appearances in Monte Carlo, Prague, and Cairo followed. Her debut with the New York Metropolitan Opera occurred in 1910, as Rosina. With that company, de Hidalgo sang in "Rigoletto" (with Enrico Caruso) and "La sonnambula" (with Alessandro Bonci) in the same season. She would return to the Met in 1924-25, for "The Barber of Seville" (directed by Armando Agnini), "Rigoletto" (conducted by Tullio Serafin), and "Lucia di Lammermoor" (with Beniamino Gigli). Following that New York debut, she sang in Florence, in "Linda di Chamounix" and "Don Giovanni" (as Zerlina, opposite Mattia Battistini). She also portrayed Rosina in Rome, in 1911. The soprano sang, as well, with Giuseppe Anselmi in "Rigoletto", in St Petersburg, in 1913.