Demi Lovato must have had bitter-sweet feelings about returning to South America for Brazil’s Z Festival. She was touring South America in November 2010 when she slugged a dancer in a rage and landed in rehab.

She talked to the screaming crowd about the incident during her show. “Over the past two years, I’ve gone through a lot of stuff, and I had to be honest about everything I was going through,” she said.

“I went to a treatment center and I was in for a number of things. Normally it’s not something someone in the spotlight would talk about. But I know there are young girls and guys that are struggling with the same things I struggled with,” she added.

Lovato, then 18, was opening for the Jonas Brothers Band on their South American tour. The singer was furious after Jonas’s Dad, Kevin, found out about her late-night partying after a tour curfew.

Lovato, now 20, believed dancer Alex “Shorty” Welch had “ratted” her out. She confronted Welch and turned violent when Welch denied talking. She puched Welch in the face and give her a bruised eye. The dancer did not fight back.

The next day, Lovato left the tour and headed for rehab to “seek medical treatment for emotional and physical issues,” a rep said.  She emerged from treatment two months later and launched a remarkable turnaround.

She took responsibility for her actions and talked openly about her problems with body image, bulimia, cutting and revealed that she was bi-polar. Now she is a judge on the American version of “X-Factor.”

The singer, who has gained about 30 pounds since exiting rehab wore black leather trousers and a spike studded leather jacket on stage. The show was the final date of her Demi Lovato Summer Tour 2012.

She urged those in the audience who were suffering from “self harm, or an eating disorder, or a mood disorder or substance abuse, to reach out and get help.”

Lovato looked at the top of her game; her performance was high-energy and she looked totally in her element. Check out the videos below, and click here to follow TheImproper on Twitter for more music updates.