In 1937, a year before the release of That Certain Age, Hollywood produced a film called Maytime in which Jeanette MacDonald sang and performed Les Filles de Cadix. In my opinion, Deanna Durbin's vocal interpretation was superior to Jeanette MacDonald's. I was inspired to research this song after I heard an orchestral version being aired on a classical music station.
-NW

Deanna Durbin - Les Filles de Cadix (Léo Delibes) - 1938
Vieux Disques
Dec 13, 2009
https://www.youtube.com/watch?v=svGUDR3YO4Y

The Maids of Cadiz (Les Filles de Cadix) (Delibes) Featuring Deanna Dubrin in her film "That Certain Age"
(Sung in French, Orchestra under the direction of Charles Previn)
Disque Brunswick n°02705-A / mx. DLA.1695

Although the film 'That Certain Age' dates from 1938, the song 'Les Filles de Cadix' was written much earlier, in the 19th century. Its composer was Léo Delibes (1836-1891), based on a poem by Alfred de Musset (1810-1857)."

Viewer comments:

@veronica3755
Toujours de trés belles images, une voix magnifique sur la musique d'un grand compositeur ! Vraiment parfait ! Merci!!
(Eng: "Always beautiful images, a magnificent voice set to the music of a great composer! Just perfect! Thank you")

@peterfarrar9015
"Les Filles De Cadiz, was outstanding & her french was impeccable. The french song is very difficult to perform. However, there are no musical mount Everests she cannot conquer. I listened to leading sopranos, jane powell, jeanette macdonald, gloria jean,& many others, with "Les Filles De Cadiz," they were all obliterated into silence & cast into the dark shadows of dire failure in trying to match the world's greatest soprano, the incomparable beautiful Deanna Durbin, with this french song. Golden words by Peter E. Farrar.