AceShowbiz - The Disney star, Demi Lovato checked into a treatment centre to deal with a number of issues, including anorexia and bulimia, self-harming and bipolar disorder, and she has one person to thank for giving her the strength to fight through her personal struggles - Madison De La Garza - her nine-year old half-sister, who plays Eva Longoria's daughter on the hit U.S. TV show "Desperate Housewives".

In an interview with U.S. news show "20/20", which will air in its entirety on Friday, she says, "I had to think of her (Madison) all the time when I was really, really rough. But I just kept thinking, 'OK, set this example for your little sister'."

"There were days where I didn't want to get out of bed, but looking at a picture of my little sister on my little bulletin board was one of the main things that kept me going."