If you insult Justin Bieber, you better believe his Beliebers will be after you! Olivia Wilde learned that the hard way when she tweeted that the 19-year-old pop star needed to "put a f---ing shirt on." Well, on Tuesday, Jason Sudeikis' fiance talked about her feud with the Biebs -- and the backlash from his fans! -- on the "Tonight Show with Jay Leno."

"This started because Justin Bieber went out without his shirt on...and he was in London, and it's so cold there and I was concerned," she said. "I have a 19-year-old brother in London, and it's freezing! And if I saw him without a shirt, I would tell him to put it on. So I told Justin Bieber, 'Put your f--king shirt on.'"

Let's be nice to the Biebs. He's had a rough month so far!

"I said it with love!" the "Incredible Burt Wonderstone" star said with a smirk. She then quipped that "people misunderstood and thought it was mean-spirited. They didn't understand it was said with love!"

The 29-year-old actress "got a lot of interesting feedback from (Justin's) fans." Joking that she heard from "about 35 million (people)," Olivia read aloud some tweets directed toward her.

Justin's hamster Pac dies

"One of them was, 'Are you a lesbian, or are you too old?' And it's great -- because it's a question I'd never asked myself before," she deadpanned. "And I was wondering, am I too old to be a lesbian?"

Another fan told Olivia to "Put your shirt over your mouth," which she plans to use as a "Shakespearean insult" later on.

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• See Olivia Wilde's sexy showgirl photo from Vanity Fair

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Her name was Lola Olivia. She was a showgirl ... Yes, that's actress Olivia Wilde heating up the pages of Vanity Fair's upcoming Hollywood issue in super-sexy showgirl garb.

Vanity Fair

Olivia Wilde as a showgirl in Vanity Fair.

Vanity Fair

Ben Affleck, Emma Stone and Bradley Cooper appear on the cover of Vanity Fair's March issue.

The annual star-studded issue features photography by Bruce Weber and 75 celebrities, including Tom Cruise, Halle Berry, Tom Hanks and more.

But it's Wilde's photos that are earning the most buzz. In the showgirl shot, she wears a glittery bikini-style outfit, tall sparkly heels and giant feathers on her tush.

In a second shot, Wilde is a bit more covered up as a still-sultry magician holding a rabbit. She plays an aspiring magician in Steve Carell's upcoming movie, "The Incredible Burt Wonderstone," which opens March 15.

The Hollywood issue will be on sale nationwide on Feb. 5.

Related content:

• Olivia Wilde's engagement ring on display in Rome
• Olivia Wilde is engaged to Jason Sudeikis
• Trailer: 'The Incredible Burt Wonderstone'

Just days after Olivia Wilde and Jason Sudeikis made their engagement official, Wilde did precisely the thing engagement ring-watchers were hoping: she stepped out with the bauble in full view.

INF

Olivia Wilde's new engagement ring from Jason Sudeikis is visible during a visit to Rome.

In Rome to film her latest movie, "The Third Person," Wilde's left hand was caught by photographers. A rep told People the ring, which appears to feature a brilliant-cut diamond, is an antique.

Sudeikis, a "Saturday Night Live" alum, and Wilde, have been dating since November 2011. According to People, the engagement came shortly after the holidays and a source close to the couple told the magazine they are "so excited and very, very happy."

Although the couple have been fairly tight lipped about their romance, Wilde has recently been more open about it. On Sunday she mentioned her engagement saying, "Thanks for all the sweet congratulatory love, friends! And may I compliment your savvy use of that nifty engagement ring emoticon."

And on Tuesday the actress traded jokes with Ellen DeGeneres with this tweet: "'@TheEllenShow: Jason Sudeikis and @OliviaWilde are engaged! ... I hope this helps him get over me.' No, but I'll wear my Ellen hat to bed."

Dave Kotinsky / Getty Images file

Jason Sudeikis and Olivia Wilde in New York in November.

Olivia Wilde and her hilarious "Saturday Night Live" beau Jason Sudeikis are officially taking their relationship to the next level!

A rep for the 28-year-old actress confirms to E! News the couple, who have been dating since November 2011 and live together, are officially engaged.

And good thing, because Olivia Wilde considers boyfriend Jason Sudeikis the love of her life!

According to People, the engagement came shortly after the holidays and a source close to the lovebirds tells the mag they are "so excited and very, very happy."

The news comes just after Olivia personally took to Twitter to deny engagement rumors back in December. The "People Like Us" actress took it upon herself to tweet: "No I'm not engaged but I AM at the Stones show and holy @!$%# Ronnie Wood you got style, boy. It's just a fact. Trying to score a shoe pic."

We're glad she got her engagement after all!

And now, where's that ring pic?!

In anticipation of Olivia and Jason big day, check out these other celeb weddings we can't wait for!

Related content:

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Pascal Le Segretain / Getty Images

Before Olivia Wilde began dating "Saturday Night Live's" Jason Sudeikis, the 27-year-old beauty was linked to a bevy of Hollywood hunks, including Justin Timberlake, Bradley Cooper and Ryan Gosling.

In the April issue of British GQ, the "Butter" star explains how being such a man magnet has affected her acting career.

PHOTOS: Hollywood's biggest flirts

"I was very sexually mature at a very young age," Wilde says. "I was very comfortable with it and talking about it, and once someone hears a young woman speak candidly about sexuality, it's like, 'Whoa!' You get labelled."

PHOTOS: Olivia Wilde's best red carpet looks

Wilde even "pulled out" of the Linda Lovelace biopic because she wanted to be viewed in a different light. "I decided that it should go to someone who is not already sexualized by the public -- Linda Lovelace was an innocent. Amanda [Seyfried] will do an amazing job."

The actress also opens up about her 2011 divorce from Italian prince Tao Ruspoli, calling it a "peaceful parting" because "there were no kids involved."

PHOTOS: Sad celebrity breakups

"We could see it as this wonderful chapter," Wilde tells British GQ. "And anyway, you fall in love again. Oh God, to think that you only fall in love once in your entire life is such a depressing thought."

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Frederic J. Brown / AFP - Getty Images

We're off to a fresh start this week in Celebrity Sightings, our daily slideshow tracking the comings and goings of stars on and off the red carpet.

Olivia Wilde, above, took in a special screening of the film "Butter" at Grauman's Chinese Theater in Hollywood, Calif., on Sunday. Meanwhile, Christian Bale was suited up as Batman for filming of "The Dark Knight Rises" in New York. Also, Kanye West and Jay-Z performed in East Rutherford, N.J., as part of their "Watch the Throne" tour.

For more images, check out the slideshow here.