Selena Gomez lip-syncs, yells 'what the f*ck' at Jingle Ball 2013 [WATCH]: Ariana Grande disses songstress? Twitter fans slam Justin Bieber's ex for epic performance fail

Perhaps Selena Gomez didn't make Santa's "nice" list this year...

During her 2013 Jingle Ball performance on Friday evening in LA (Dec. 6), it was clearly obvious that the "Come & Get It" songstress was lip-syncing.

Apparently during her opening song, Gomez suddenly yanked-out her in-ear monitors (devices that help performers hear themselves sing during live sets) and attempted to go on without them. That didn't work out so well...

According to Hollywood Life eyewitnesses, the 21-year-old starlet went from "visibly angry to verbally angry" when her microphone went live... a big no-no when lip-syncing. Gomez was then heard yelling, "What the f*ck?"

Things got very Ashlee Simpson-esque from there. Gomez couldn't continue until backing tracks were fixed, which made it even more obvious that she wasn't actually singing. The stage suddenly went dark, and Justin Bieber's ex quickly walked-off.

Gomez promptly returned to the stage after things were finally resolved, and apologized to the crowd for "sound issues." She promised two more songs, but couldn't even make it through her hit tune "Come & Get It." After that, she ran back off the stage and didn't return.

Oops.

Twitter fans later called Gomez out on her epic lip-syncing fail:

@katherinejoyce: "I like Selena Gomez, but seriously, she can't sing live & the worst part about that is that she can't even lip-sync properly."

@jxstinlove: "kinda feel bad for Selena Gomez but then again if she knows shes gonna lip-sync why didnt she check and see if it worked? lmaooo come on."

@buteruhh: "Artists usually get caught when they lip sync so idk why Selena decided to."

@jdbvibxs: "selena's lip sync failed forever laughing."

Lip-syncing is a pretty common thing nowadays... especially with performances that require an intense dance routine. Do Mstars fans blame Gomez for the screw-up?

Following the rather embarrassing live performance slip-up, songstress Ariana Grande hit the stage and experienced similar audio difficulties. But according to Hollywood Life, Grande did NOT lip-sync despite having bronchitis - "she sang 75 percent of her first song without the proper audio."

After her set, Grande shouted, "At least you know I wasn't singing to a track!"

Ouch.

But apparently, the former Nickelodeon starlet wasn't "throwing shade" at Gomez:

@ArianaGrande: "Ohhh jesus. I wasn't throwing shade AT ALL I didn't even see anyone else's set. I was sick backstage that's why I didn't even do the carpet."

@ArianaGrande: "I was just cracking a joke cause my mic was off. Everyone had tech difficulties. Sorry if it was taken the wrong way it wasn't my intention!"

What do Mstars fans think about all the Jingle Ball drama?