(Cover) - EN Showbiz - Demi Lovato has denied that her much publicised meltdown was "over a guy".

The 18-year-old entertainer opened up in the September issue of Elle magazine and said that her breakup with pop star Joe Jonas was not the reason for her unravelling and ultimately ending up in rehab.

She said her problems were a lot more complex and not just specific to one issue.

"I wouldn't credit my meltdown to a guy. There was so much other stuff in my life," the actress said.

Joe broke up with Demi in May 2010 and quickly moved on to dating Ashley Greene which left the teen star heartbroken.

But Demi, who turns 19 later this month, does admit to being out of control when she hit her tour mate Alex Welch.

"I was completely out of line all summer. Just the worst attitude totally ungrateful... I just felt like she'd betrayed me. That's the bottom line. When you punch someone on a plane, enough is enough," she explained. "Right after, I texted my mom and just said, I'm sorry.'"

Demi spent three months in rehab at the end of last year for bulimia and self-harm and admits her body issues stem from her childhood.

"Those girls never gave me an explanation for why they were bullying me," Demi said. "One of the words they called me was fat. At that age, you think, Oh so I don't have friends because I'm fat.'"

The singer also regrets how a picture of her with cutting marks on her wrists was handled.

"I don't think I would have been ready to talk about [my problems] then, but I could've come up with something better than gummy bracelets. Needless to say, that publicist is no longer with us... (pause). I mean she's alive." (C) Cover Media