Jessie J recently performed "Bang Bang" at the 99.7 NOW!'s 2014 Triple Ho Show at the SAP Center in San Jose, Calif. without Ariana Grande and Nicki Minaj but she was not alone. "Really Don't Care" Demi Lovato sang Grande's part.

At first, Jessie J sang solo but the audience was surprised when Lovato stepped out onstage wearing a black crop-top and skirt to sing Grande's part. Neither of them rapped Minaj's verse. Instead, they both dance while the rap verse played, Hollywood Life reported.

After their performance, Lovato tweeted, "That just happened..... Thank you SO much @JessieJ for having me on stage for Bang Bang... It was an honor!"

Jessie J also took to Twitter to express her appreciation of Lovato's performance. She tweeted, "WOW!!! @ddlovato is a dream to be on stage with!!! Thank you girl!!! You sang yo ass off!!! #bangbang..."

During the American Music Awards on Nov. 23, Jessie J, Grande and Minaj performed "Bang Bang," which is currently at number 14 on the Billboard Hot 100. Before Jessie J hit the stage, she danced with Taylor Swift, Lorde and Khloe Kardashian.  

Meanwhile, Lovato revealed that she found herself straying from her healthy eating habits so she almost went back to rehab for an eating disorder.

In a recent interview with Fitness magazine, Lovato said she was "obsessing over food and terrified of it at the same time" and her boyfriend Wilmer Valderrama noticed and called her out on it, "which was a relief."

"I was done being afraid of food and so tired of overeating and not knowing why I did it. Now I'm on a structured meal plan. I eat four small meals and two snacks a day. It's teaching me portion control," Lovato added.

The 22-year-old singer said her current motto in life motto is "If Beyoncé can do it, I can do it" and added that she supports women with curves, such as Jennifer Lopez, Iggy Azalea and Kim Kardashian.