X Factor star Katie Waissel is reportedly at war with mentor Cheryl Cole.

According to¬†The Sun, the contestant is furious that Cheryl wants her to perform¬†‘The Bitch Is Back’ for tonight’s Elton John theme and took it as a personal insult. She has since insisted on singing ‘Saturday Night’s Alright (For Fighting)’.

She told the paper: “There were a couple of songs put forward to me. I liked the fighting spirit of the songs, but one goes a little too far. Do you know what? You can push things too far.”

A source added: “To say Katie is a diva is putting it mildly – she’s a complete nightmare. She is so rude to people and treats staff on the show like dirt. Cheryl has been livid with the way she’s been acting.

“She’s done her best to help her, but she still gets this rude backchat from her. And Katie isn’t honest with anyone. She fled to meet Amy Winehouse the other night and when we asked about it she just lied and said she didn’t.”

The report also claims that Waissel is unhappy with the amount of attention that Cole is giving to Cher Lloyd.