Outspoken Mel B clashed with the other judges on Monday night's show, labeling a performance "cheesy" after the others had gushed about it.
"What are you talking about?" snapped Nat, copping a killer side-eye from the Spice Girl in response.
But Mel B says the rivalry is only for the cameras.
"We're all feisty and we're all in the competition to win it so we're not shy in saying what we feel," Mel told The Daily Telegraph.
"But we also know it's a TV show so once we're backstage, we have a laugh and hang out so it stays at the [judges'] desk."