'Skyscraper' singer Demi smoulders in the new issue of the iconic magazine (on newsstands 6 May), showing off blonde hair and a sexy smoky eye while explaining how her younger sister was the inspiration behind her role model status.
"When I was younger, I needed someone in the spotlight to idolise, who stood for positivity and light and happiness, and wanted to change the world. And because I didn't have that, I realised, I want to do that, if only for my 12-year-old little sister."
The star's little sister is Madison De La Garza, who appeared in Desperate Housewives as Juanita Solis.
Demi is well known among her fans for promoting strength and happiness, and being open about her own struggles with issues such as body image and addiction in the past.
The 21-year-old found fame as a child in Disney's Camp Rock movies and TV series Sonny With A Chance, but her life began to spiral out of control and she ended up in rehab to treat her substance abuse problems and tackle an eating disorder.
Since leaving rehab in 2010, she's turned her life around, enjoying huge success with her music career and enjoying a stint as an X Factor USA judge.
Despite all her success, she's still got big dreams for the future: "I'm very proud of how far I've come, but I definitely want to win a Grammy one day, and I dream of winning an Oscar. I want to continue to tour and build my fan base and make music that will last for decades."
As for when she feels sexiest, the low-key star said: "I feel sexiest when I'm comfortable – this means when I'm in my element onstage, and also when I'm wearing a T-shirt, jeans, my leather jacket, and no makeup!"
For more on Demi Lovato visit the Cosmopolitan for Latinas website.
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Watch Demi's video for 'Skyscraper' below: