Pretty sure...according to the Wiki page for the show: " February 20, 2013, it was announced that former Spice Girls member Melanie Brown (aka "Mel B") would replace Sharon Osbourne as the third judge."
I've got pics of her (and Howard Stern and the other judges at the show's taping). My friend's daughter is the head wardrobe person for that show (and for others, Sharon Osbourne, Nick Canon, etc.)... so yea, I'm fairly sure.
So Mel B was in the Spice Girls and the Dixie Chicks?