[2] Her professional debut came the following year with West Palm Beach Opera, where she sang Susanna in Mozart's The Marriage of Figaro.
[1] From 1976 to 1978 she was a member of the Staatstheater Kassel,[3] where her repertory grew to incorporate such roles as Liù in Puccini's Turandot, the title role in Massenet's Manon, and Zdenka in Arabella by Richard Strauss; she also participated in performances of Unter dem Milchwald by Walter Steffens.
[4] In earlier years, Daniels possessed a lyric voice, and her repertory encompassed such parts as Adèle in Rossini's Le comte Ory, the title roles in Handel's Agrippina and Puccini's Madama Butterfly, Mimì in La bohème, the title role in Smetana's The Bartered Bride, and Marguerite in Gounod's Faust.
Later in her career her voice became more powerful and dramatic; in 1991 she performed Minnie in Puccini's La fanciulla del West at the Metropolitan Opera, a role which has come to be seen as her finest portrayal, and she added the title roles in Puccini's Tosca and Manon Lescaut, and the Marschallin in Der Rosenkavalier by Richard Strauss to her repertoire.
She continued her career into the 1990s with roles such as Nedda in Leoncavallo's I pagliacci and Senta in Wagner's Der fliegende Holländer.