Apparently, when some young stars see other stars' kissing, they want to throw up.

Well, this was the case for Taylor Swift, catching a glimpse of Justin Bieber and Selena Gomez rekindling their romance with a kiss. According to the Los Angeles Times, the singer, who cleaned up with several awards at the 2013 Billboard Awards, also felt dirty in seeing the former lovebirds' get some lip action backstage on Sunday night.

But wait, Gomez and Swift are BFFs so why the disgusted face? Her stuck-out tongue and stank expression said that Bieber was not welcome to "come and get it" when it comes to Gomez. What Swift saw was only a hug and peck on the cheek between the two exes, but that was enough to flash a face that looked like she just ate some sour patch kids candy.

Well, she could have been mad that Gomez was dipping back to her old goodies after declaring she was newly single and Bieber free. Could this spell a reunion for the young one-and-off-again couple?

It's hard to say, but Swift had nothing to frown about given that she won eight awards. Could she have cut Bieber some slack after fans booed him for winning the first-ever Milestone Award, which Swift was competing to win, too?

To check out Swift's reaction to the "disgusting" PDA, see the clip below!