Lagier was born in Dunkirk on 30 November 1833, in the Rue du Magasin à Poudre, but grew up in a boarding school in Paris[1] and her father was a musician.

[1][2] In 1865, unusual for the time, she signed a contract with the theatre café-chantant (café-concert) Eldorado, a counterpoint to the growing popularity of singer Thérésa.

[1][2][3] She continued to sing while returning to theatre regularly (both in Paris and Saint Petersburg) until 1880, when she married the tenor (or possibly baritone) Eugène Dufriche in London.

However, she received sharp criticism from the French newspaper Le Figaro — the collaborator of the magazine, Alfred Delvau, about the name "la grasse", referring to the guttural pronunciation of her R's.

[1][2][4] Lagier was also the subject of some caricatures,[1] including a satirical newspaper La Lune depicting her and Thérésa.