Educated privately as a child, she was sent to Paris at age 16 to study at the Paris Conservatory, following the breakup of her engagement to American journalism pioneer William Randolph Hearst.

In 1887, a chance meeting with a musical prodigy and one of the most highly regarded musicians in Europe—Jules Massenet—served as the catalyst to her stellar, decade-long success there. She became the first American singer for whom the major European composer Massenet wrote operatic works. Massenet, enraptured by Sanderson’s beauty, three-octave range, temperament, and histrionic ability, crafted Thaïs and Esclarmonde specifically for her. He also reconstructed his Manon to feature her high voice and to allow her to reinterpret the title role.