The 29-year-old singer, who was signed by Cowell for his SyCo/Sony label after winning 'The X Factor' in 2006, said there are no hard feelings between the two, after she broke her new multi-year deal with Island Records behind his back, reported Female First.
"I was offered another deal with Syco but I thought it was time to have a new team with fresh ideas. I have spoken to Simon. He is sad I didn't stay with Sony but he is happy for me and proud," she said.
"It is like leaving home almost. You have to be like, 'Later, mum and dad'. I am doing my own thing now.," she said.
Lewis said Cowell gave her a great launch pad and she felt it was time to start somethign new. "Now I'm able to spread my wings, fly and make something for myself," she added.
Though rumours emerged Simon, 54, felt snubbed by Lewis, he previously took to Twitter to congratulate her on her new contract and thanked her for for putting 'The X Factor' "on the map".