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Demi Lovato, Nick Jonas, Joe Jonas, Wilmer Valderrama

Instagram, iHeartRadio

Demi Lovato's concerts aren't just performances, they are events!

Such was the case Friday night when the "Confident" crooner arrived on-stage to perform at the iHeartRadio Music Festival at the MGM Grand in Las Vegas.

Wearing an edgy, sheer Yousef Aljasmi jumpsuit with knee-high boots and a furry jacket, the 23-year-old got the crowd on their feet when she performed her hits including "Cool for the Summer" and "Heart Attack."

What got fans extra excited, however, was when cameras caught boyfriend Wilmer Valderrama, ex-boyfriend Joe Jonas and great friend Nick Jonas supporting their girl together in the audience. The guys were even caught rocking out to "Really Don't Care."

"Wilmer thinks she is extremely gorgeous and loves watching her perform and spending alone time together. He loves her voice and is her number one fan," a source revealed to E! News. "He was really proud to see her perform last night and they had a really nice time after together in Vegas."

The biggest surprise of the night, however, may have come when Lovato invited Third Eye Blind lead singer Stephan Jenkins on-stage for a surprise collaboration of the ‘90s hit "Jumper."

"Everybody give it up for the incredible Stephan Jenkins," she told the crowd before sharing a hug with the rock star.

Friday night only marked the beginning for the two-day festival. Jennifer Lopez, Blake Shelton and others are scheduled to perform Saturday evening. In fact, fans can watch the concert event in a two-night special on The CW Sept. 29 and 30.

As for Demi, she was back on stage Saturday afternoon performing at the iHeartRadio Music Village after a night that saw her face-to-face with Diddy, Lil Wayne and countless others.

"Diddy & Weezy sandwich," she wrote on Instagram over the weekend. "#legitsquadgoals #legends #iheartradio."