The 'Bleeding Love' singer - who shot to fame after winning the music mogul's UK TV talent show 'The X Factor' in 2006 - admitted she has remained close to her mentor, but is still nervous about how he will react to her music.
Speaking about recording some new material, she said: "He didn't come to the studio but I'd play him songs down the phone. It's scary and you think, 'Please like it!'
"We've formed more of a bond and we can be honest with each other."
She said: "I have a relationship with the McCartneys. I respect their values and their opinions about vegetarianism because I'm a vegetarian. They're really cool people."
However, despite her successes, the singer admits she still gets overwhelmed when she meets other celebrities.
She added: "I was star-struck when I met Samuel L Jackson and Daniel Day-Lewis at the Golden Globes. I was excited when I met Nelson Mandela, too. I performed at his birthday in 2008. I was really honoured."