Demi Lovato Clashes with Simon Cowell on 'X-Factor,' Songstress Meets President Obama and First Lady at 'Christmas in Washington' [VIDEO]

Things are heating up on the "X-Factor," especially between feuding judges Demi Lovato and Simon Cowell. On the Dec. 5 episode of the hit singing reality show, tensions reached an all-time high when Lovato bashed Cowell's beloved trio Emblem3, and the former "American Idol" judge didn't take the heated insults sitting down! But after the on-air clash, the 20-year-old songstress appeared to take a humble step back when she had the privilege of meeting President Barack Obama and his First Lady Michelle at the White House's annual "Christmas in Washington" concert on Dec. 9. Read on for more details.

It looks like Lovato foresaw her personal favorite contestant CeCe Frey getting the boot on Thursday evening's "X-Factor" elimination show, so decided to take out her aggression on Cowell the night before. When the 53-year-old's group Emblem3 performed a cover of Bruno Mars' "Just the Way You Are," fellow judges Britney Spears and L.A. Reid responded in a rather positive, praising light. But not Lovato - she bashed the performance, saying it felt like "a downgraded version of the Jonas Brothers five years ago." And Cowell was not too pleased.

"That was incredibly dumb, what you just said," Cowell snapped back at Lovato. "Honestly."

Lovato kept bugging Cowell throughout the episode, constantly attempting to steal his mic and bashing Emblem3 again when they hit the stage for a second time to perform the classic hit "Forever Young." The blunt Brit didn't even know how to respond to Lovato's odd behavior, eventually questioning, "What is the matter with you tonight?"

Lovato finally had something nice to say when Cowell's all-girls group "Fifth Harmony" took the stage to perform the former Disney star's hit tune "Give Your Heart a Break." According to Lovato, "I think this song should have been your song... It was energetic. It was fun. I think that Simon actually did a good job this week."

Cowell's reaction - "Thank you, Cruella... This is what we've been trying to do to show that you are a legitimate girl group." Even so, Cowell wasn't too pleased that America chose a Lovato song for his group to play... but Lovato herself sure was:

What do Mstarz fans think of Lovato and Cowell's love-hate relationship - is it just for TV, or does the songstress really hold a grudge against her fellow veteran judge?

In other, happier Demi Lovato news - the songstress was beyond thrilled to receive the privilege of meeting President Obama and the First Lady at the annual "Christmas In Washington" concert to benefit the Children's National Medical Center.

Lovato and other big-name celebs including Diana Ross, Megan Hilty (from "Smash"), "Gangnam Style" rapper Psy, and American Idol winner Scotty McCreery performed with several choir singers from DC at the National Building Museum on Sunday, Dec. 9. Lovato later posted on Twitter:

@ddlovato: "OH MY GOD... I just met the PRESIDENT OF THE UNITED STATES!!!!! Our First Lady is GORGE. So excited right now!!!... Such an honor singing for the President and the First Family."

The "Christmas In Washington" concert airs Dec. 21 on TNT.

Wonder if Lovato will finally lighten up on the "X-Factor" considering it's around the holidays?