Well, now, wait a minute. Didn't the Opéra Comique first try to cast a soprano in the role? And when she said no, the role was given to a mezzo? That would indicate the score was originally written for the higher voice. So when the higher passages were added to the published score, maybe that was just restoring what had been cut to accommodate the lower voice. Meaning the added bits were written by Bizet after all. Could it have happened that way?