Demi and Miley met on the set of Hannah Montana in 2007 and became fast friends. Two years later, they had a very public spat, taking to Twitter to air each other's dirty laundry. Miley shared a photo of the two with the caption, "Now this is what true friendship looks like. None of that hollywood c***. @ddlovato I miss you." To which Demi shot back, "Yeah... It's just kind of hard to miss somebody that I don't know anymore."
Demi's semisnide comment could have been due to the fact that Miley had recently filmed a YouTube video where she mocked Demi and Selena Gomez (Miley later took the clip down and said that she was "super sorry" in an interview). Demi addressed the fight in an interview with Seventeen magazine in 2012, saying, "[Miley] and I are strong headed. When we fight it’s brutal, and we’re like, ‘We’re never going to be friends again!’ Then two days later, were like, ‘I love you and I miss you!'"
It seems that despite their tumultuous past, Demi and Miley are on good terms. Most recently, Demi, who has had her own personal ups and downs with drugs and alcohol, spoke out about her pal's new party lifestyle in an MTV interview, saying: "She knows how I feel about the whole partying thing. I love her to death, and I’m always like, ‘Just be careful.' I care for her so much that I’m so protective. But she’s good. She’s got a good head on her shoulders."