The 21-year-old singer believes checking into rehab for addiction issues and an eating disorder in 2012 helped cushion the transition from being a Disney child star to a mainstream pop artist for her.
Asked why she didn't leave Disney and develop a raunchy image, she said: ''I guess my transition was a little easier because I went straight to rehab. I didn't twerk - I just went to rehab!
''But you know what, I think the world needs to get over the fact that [Miley] was Hannah Montana when she was 16.
''Nobody knows her. Nobody really knows who I am, and the same with Selena [Gomez] and Jonas [Brothers] and everyone that has grown up in front of the public eye. We're adults now.''
Demi admires her friend's guts for building such a strong image, but worries that her hyper sexualised, tongue-waggling persona is ''overshadowing'' her talent.
She told We Love Pop magazine: ''I think she knows what she's doing. A lot of artists take that route of shock value and that's fine, but I think she has such an incredible voice that's overshadowed by some of the things that she's doing.
''I'll always love her - she's been one of my friends since I was 14. But everyone is on their different journeys and she's having fun, she's being who she is - so power to her.''
His new album Underneath It All is out now.