The 27-year-old was dropped from the US show last week and is said to have snubbed Cowell's offer of more money to return to the UK programme because she didn't want to run the risk of becoming like his close friend Sinitta, who was Cowell's protégé in 1986.
According to The Sun, Cheryl's mum Joan told a friend, 'She was terrified Simon had become her puppet master and she was being turned into his new Sinitta - Simon's little pet.
'She is determined to carve out a career without him. He'll have to come up with something special for them to even speak again.'
A second source added, 'Simon made Cheryl a UK superstar. She became the nation's sweetheart. But after he dumped her in the US, she decided to make a stand to show she's not a needy puppy.'