The 19-year-old battled a number of personal problems, including an eating disorder, depression and self-harming, but she has since bounced back and recently declared she is happier and healthier than ever. But Lovato insists she wouldn't have made such a quick recovery if it hadn't been for her two closest pals.
She tells Billboard.com, "I feel like there are some people that you're friends with that talk to you on Twitter or you text, but the people that are really there for me are the people that were there for me when I went into treatment.
"The people that were calling me while I was in there were Kim Kardashian and Selena Gomez. Those two girls, they meant the world to me. They still do."
Lovato, who attended Kardashian's August wedding to Kris Humphries, adds that the reality TV star has been "like a big sister" to her.
Demi's album 'Unbroken' is in stores right now. Make sure to get a copy!