Lovato, 19, checked into rehab and Kardashian, 30, was there for her the whole way through.
Lovato was working through her eating disorder and other issues when she sought treatment.
The Disney star told Billboard.com: “I feel like there are some people that you're friends with that talk to you on Twitter or 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.'