According to Cheryl Cole's mum Joan, it was Cheryl's decision not to return to the X Factor in the UK after her dismal reception in the US. Joan says "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."
To be fair, ending up like Sinitta would be a fate worse than death, but the whole situation reeks of trying to limit the humiliation levels. By taking ownership of not coming back to the X Factor Cheryl can try to reclaim some autonomy and individuality away from the Cowell talent-making machine, but at the risk of cutting off her nose to spite her face.
You know when two people break up, and then one of them hacks into the other's facebook account and leaves messages like "I only went out with you out of pity" and " your willy is tiny anyway"? Yeah. That's what this looks like right now.