The New Grove Dictionary of Opera (Hugh Macdonald) says that Bizet worked on the score in 1873, and at the end of that year Célestine Galli-Marié (a mezzo) was engaged to sing the title-role, which she did when it opened in March 1875. Bizet died on the night of the 33rd (of 45) performance. Absolutely no mention of sopranos having been approached.