It was confirmed last month that the 17-year-old had signed with Sony, but according to the Sunday Mirror, SyCo landed the deal ahead of other Sony labels Epic, Colombia and RCA.
The paper claims Simon is keen to oversee Ella's career, and intends to make the young singer a global star and millionaire by next year.
An insider told the tabloid: "He was always a big fan of Ella's and watched her from the US, he thought she would win and he'd automatically get her.
"He wouldn't usually sign someone who came sixth, usually he would have forgotten about contestants kicked off so early but he was overwhelmed by Ella's talent. He admires her maturity."
The source also suggested that SiCo believes the soulful singer - who was voted off The X Factor after a sing-off with eventual winner James Arthur - could be the next Adele, and will encourage her to keep writing her own material.
Ella reportedly met with Cowell earlier this week, and is excited about beginning her music career.
She told the Sunday Mirror: "I've already written stuff but I can't wait to pen new material because I haven't written all through the period of being on the X Factor."