The My Heart Will Go On singer turned into a mega-diva during her turn on the NBC show as a guest mentor.
"Céline acted like she was a superstar the moment she walked on set to tape her episodes," says an on-set snitch.
"She was extremely entitled and was just not friendly or welcoming to the production crew at all!"
Accompanied by a huge entourage of people at the set of the show, Céline "got the royal treatment," the source claims.
“She had to do several retakes and complained about everything from her hair and makeup, to the outfit that was chosen for her.”
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