12/19/2012 11:50 pm ET Updated Dec 20, 2012

Demi Lovato Performs With Fifth Harmony On 'X Factor USA' Finale (VIDEO)

Tonight, "X Factor USA" featured the final performances from the show's remaining 3 acts: Carly Rose Sonenclar, Tate Stevens and girl group Fifth Harmony. For the second song of the evening, each was paired with a surprise superstar for a special duet. We were super excited when we discovered that Fifth Harmony would be singing "Give Your Heart A Break" with one of their "X Factor" judges, Demi Lovato.

Despite the fact that the girls have had the opportunity to speak with Demi throughout the season, her introduction to the stage from group member Camila Cabello couldn't have been sweeter and more heartfelt. "I literally can't believe that I'm about to say this, but please welcome somebody that we look up to so incredibly much, and she's amazing, and I'm gonna cry," the 15-year-old gushed.

And it seems the admiration is mutual: Demi Lovato admitted in an interview last week that she is interested in collaborating with the girls after "X Factor" is over. Watch their adorable duet -- during which Demi gave a dynamite vocal showing -- in the video above.

The other pairings of the evening were Carly Rose Sonenclar and LeAnn Rimes ("How Do I Live?") and Tate Stevens with Little Big Town ("Pontoon"). Watch Carly's performance in the video below.

Tell us: Do you think Fifth Harmony, who were the show's underdogs last week, have a real shot at winning the "X Factor" tomorrow after tonight's performances? Sound off in the comments below or tweet @huffpostteen!