Demi Lovato angry on X Factor

Demi Lovato 'was pissed' to learn that an X Factor choreographer Brian Friedman altered her acts' performances.

The US TV talent show's first live programme aired Thursday.

Demi had been working with her acts CeCe and Willie Jones extensively for over a week on their performances.

Brian reportedly changed CeCe and Willie's presentation at the last minute and Demi wasn't happy about that at all.

"Demi was pissed and told the producers this wasn''t what she''s planned and she was not putting her name to it," a source told Radar Online.

"The acts and dancers were all rushed out of the studio to make the changes 10 minutes before the show started.

"Demi had worked hard and spent all week planning performances and styling for her contestants, so to say she was unimpressed that Brian had changed things is an understatement.

"She insisted everything be changed back to what she''d planned. She''s told them all no one is to change anything on her acts ever again. She''ll be signing absolutely everything off."

According to TMZ, two performers and a handful of crewmembers fell ill after eating bad tuna and Emblem3's Drew was rushed to hospital ahead of the live show.