The 18-year-old songstress came sixth in the 2012 edition of 'The X Factor' - when Cowell didn't appear among the judging panel - but says his easygoing personality helped to calm her nerves when they met and agreed a recording contract.
The 'Ghost' hitmaker explained to The Independent newspaper: ''I don't know what I was expecting but it was such a chilled conversation, and he is just a normal guy.
''It was humbling to sit in a room with him, and talk on the same level. He said he wanted ours to be a long-term deal, and for me to take as long as I liked. He's been so encouraging all the way through.''
Ella admits that although her 'X Factor' fame has helped to catapult her into the spotlight, it's not a guarantee of long-term success.
She added: ''I don't expect anything from all this, you know. I just see it as a head start. And I'm lucky to have had it. I'm exactly where I want to be now, and I'll work hard to stay here.''
'Chapter One', Ella's debut album, is released on September 22.
The novel's author saw a cut of the film and loved each of the changes the movie's director had made.