Selena Gomez kissed ex Justin Bieber backstage at the Billboard Music Awards on Sunday night and Taylor Swift was having none of it.

Gomez and Bieber's kiss was captured on Billboard's backstage feed on Sunday night at Las Vegas' MGM Grand, Just Jared notes. The 20-year-old songstress ran into her former boyfriend while being escorted backstage by security with Swift and another female friend. When the "Spring Breakers" actress turned to give the "Boyfriend" star a kiss on the cheek, Swift glanced over and stuck out her tongue at the PDA.

Of course, the entire encounter was preserved in an awesome GIF and makes us love Swift even more.

While Gomez and Bieber chatted, Swift stood alongside and appeared to sigh as she waited for her bestie to finish up with her on-again, off-again beau.

Earlier in the night, Gomez and Swift sat together in the front row and watched while Bieber got booed accepting the Milestone Award. Gomez's kiss at the end of the night might've just been a little TLC to make Bieber feel better after he had to defend his "craft."

Last week, Gomez and Bieber were spotted clubbing at Supperclub in Los Angeles. They entered through a back door around 11:30 p.m. and then exited holding hands at 12:45 a.m., according to E! News.

Despite their hanging out and posting cozy Instagram photos together, Gomez and Bieber are allegedly not a couple again (yet). The former Disney star told Boston's Kiss 108 FM during a recent interview that she is single and ready to date.

She also opened up to InStyle magazine about their breakup, hinting that a reconciliation isn't completely off the table.

"You can’t help who you date," she said. "So I wouldn’t swear off that or say that’s what I want again. I don’t know. I’m a kid, and a breakup is normal. I have to go through the emotions and feel it out. I’m doing my own thing, being with my friends, and he’s doing very well too.”

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    Chris Brown performs at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Madonna

    Madonna poses backstage with her awards for top touring artist, dance album and dance artist at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by John Shearer/Invision/AP)

  • Madonna

    Madonna accepts the award for top touring artist at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Justin Bieber

    Justin Bieber, center, performs at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Chris Brown

    Chris Brown, center, performs at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Nicki Minaj

    Nicki Minaj accepts the award for top rap artist at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Tracy Morgan

    Host Tracy Morgan, center, performs at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Selena Gomez

    Selena Gomez, center, performs at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Justin Bieber, Miley Cyrus

    Miley Cyrus, right, presents the award for top male artist to Justin Bieber at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Taylor Swift

    Taylor Swift accepts the award for top Billboard 200 album for "Red" at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Carly Rae Jepsen

    Carly Rae Jepsen poses backstage the award for top digital song for "Call Me Maybe" at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by John Shearer/Invision/AP)

  • Christina Aguilera, Pitbull

    Christina Aguilera, right, and Pitbull perform at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Ke$ha

    Ke$ha speaks on stage at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Emmy Rossum, Jason Derulo

    Emmy Rossum, left, and Jason Derulo present the award for top Billboard 200 album on stage at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Morten Harket

    Morten Harket, of the musical group A-ha, performs at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Taylor Swift

    Taylor Swift accepts the award for top Billboard 200 album for "Red" at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Justin Bieber

    Justin Bieber performs at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • will.i.am

    Will.i.am presents the award for top touring artist at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • will.i.am, Madonna

    Will.i.am, right, presents the award for top touring artist to Madonna at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Kid Rock

    Kid Rock presents the award for top rap song at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Taylor Swift

    Taylor Swift, center, performs at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Selena Gomez

    Selena Gomez speaks on stage at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Tracy Morgan

    Tracy Morgan speaks at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Caroline Hjelt

    Caroline Hjelt, of musical group Icona Pop, performs at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Psy

    Psy speaks on stage at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Chris Brown

    Chris Brown performs at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Tracy Morgan, Psy

    Tracy Morgan, left, and Psy participate in a "dance-off" at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Neil Perry, Kimberly Perry, Reid Perry,

    The Band Perry, from left, Neil Perry, Kimberly Perry and Reid Perry, perform at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Neil Perry, Kimberly Perry, Reid Perry,

    Kimberly Perry, center, and Neil Perry, right, of musical group The Band Perry, perform at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Tracy Morgan

    Host Tracy Morgan speaks on stage at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Selena Gomez

    Selena Gomez, center, performs at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Selena Gomez

    Selena Gomez, center, performs at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Shania Twain

    Shania Twain speaks on stage at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Shania Twain, Nicki Minaj

    Shania Twain presents the award for top rap artist to Nicki Minaj at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Bruno Mars

    Bruno Mars, third from left, performs at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by Chris Pizzello/Invision/AP)

  • Casper Smart, Jennifer Lopez

    Casper Smart, left, and Jennifer Lopez arrive at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by John Shearer/Invision/AP)

  • Taylor Swift

    Taylor Swift arrives at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by John Shearer/Invision/AP)

  • Jennifer Lopez

    Jennifer Lopez arrives at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by John Shearer/Invision/AP)

  • Taylor Swift

    Taylor Swift arrives at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by John Shearer/Invision/AP)

  • Taylor Swift in Zuhair Murad

  • Miley Cyrus in Balmain

  • Emmy Rossum in Zuhair Murad

  • Kelly Rowland in Rami Al Ali

  • Jenny McCarthy

  • Jennifer Lopez in Zuhair Murad

  • Ke$ha in Givenchy and Palladium

  • Alyssa Milano in Emilio Pucci

  • Chad Kroeger, Avril Lavigne

    Chad Kroeger, left, and Avril Lavigne arrive at the Billboard Music Awards at the MGM Grand Garden Arena on Sunday, May 19, 2013 in Las Vegas. (Photo by John Shearer/Invision/AP)

  • Selena Gomez in Atelier Versace

  • Selena Gomez in Atelier Versace

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