Reality TV mogul Simon fired Cheryl from the judging panel of the US version of 'The X Factor' in 2011 after lacklustre performances in Los Angeles and Chicago, and while the 30-year-old singer was paid her £1.2 million wage for the series, she claims she was promised £1.5million to return for a second series, regardless of the outcome of the first.
A source told the Daily Mirror newspaper: ''She is pushing for full fees ... £2 million, legal fees and a bonus, which could total £3.5 million. Cheryl will learn what Simon earned and her co-stars too.''
Simon is set to be called to court as a key witness in the case.
The trial will reveal details of the contracts signed by all the US 'X Factor' judges' - which at that time also included L.A. Reid, Paula Abdul and Simon - which could work in Cheryl's favour if it reveals the others were treated differently to her, although Judge Abraham Klein has ruled details must be kept private.
The source added: ''Those papers could be the smoking gun if she can show others have been treated differently to her. [However], the confidentiality of the of discovery order means much of his testimony is unlikely to become public.
''Every aspect from pay, expenses, contracts and personal requirements of the stars will be released.''
Even if Cheryl, who has refused to settle with the show's production company, Blue Orbit, wins the case her payout will be kept confidential. However, if she loses she could face £1 million legal costs plus paying Blue Orbit's court fees.