The 'Heart Attack' hitmaker - who sought treatment for an eating disorder, drug abuse and self-harming in December 2010 - has praised her best friend for seeking help after it was revealed she spent two weeks in rehab last month.
Demi told E! News: ''Selena is... I've known her for 14 years and we've been best friends. She's amazing. I love her.''
Asked how Selena is doing, the 21-year-old star replied: ''We're best friends but that's all of her business and I just want to let her do her thing. She's amazing, I love her.''
The pair - who struck up a friendship when they starred on 'Barney & Friends' when they were children - were spotted enjoying dinner together at Craig's Restaurant in west Hollywood following Selena's stint in late January.
Demi also tweeted her support for Selena, who was struggling to get over her ex-boyfriend Justin Bieber and allegedly drinking more than usual before seeking help, on Wednesday (05.02.14), writing: ''Weakness is living in denial. Only the strongest people ask for help.''
A representative for the 21-year-old star confirmed Selena had spent a fortnight with Arizona's Dawn at the Meadows last month, but denied she had ''substance abuse'' problems.