Demi Lovato gives tips on dealing with 'grumpy old man' Simon Cowell


American singer Demi Lovato has said the best way to "deal" with Simon Cowell is to "treat him like any other grumpy old man on the street".

Lovato worked alongside Cowell as a judge on the American version of The X Factor for two years.

Talking to BBC Radio 1's Scott Mills, she said: "You just gotta give it back to him, you really do, you just have to give it back to him and I think people will have a lot of respect for you when you do that because Simon's not used to people talking back to him."

She also revealed she's going to be a bridesmaid for singer Iggy Azalea at her upcoming wedding.

However, she's not yet had any dress fittings. 

"I think she's taking her time with it," she explained.

Lovato has been dating That '70s Show star Wilmer Valderrama since 2011.

She is famously private about their relationship, but did reveal that when it comes to being proposed to herself, she's a traditional girl at heart.

She explained: "I'm just a little old-fashioned when it comes to that", adding: "Yeah, and you know I let him call the shots, I make a lot of decisions in my life so it's nice to kind of hand over the control to someone else."