The Insider.com

Last week, Justin Bieber, 17, shot down claims that he fathered a baby after a 2010 concert in Los Angeles. Now, get the other side of the story from the woman behind the outrageous allegations -- Mariah Yeater.

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There are several questions surrounding Mariah's story, so The Insider's Kevin Frazier conducted the first sit down interview with the 20-year-old to find out whether or not she is telling the truth.

Even though Bieber denies ever meeting Mariah, she claims to have been introduced to Bieber backstage at Staples following one of the pop star's performances.

Mariah went on to claim that she saw a different side of Bieber during their alleged sexual tryst.

"When we got to what turned out to be a bathroom, his whole demeanor changed," said a tearful Mariah, who claims to have proof that Bieber fathered her son. "It went from cute and gushy to, just, more aggressive."

While Mariah continues to stand by her story, a source who worked with the Bieber camp that night tells The Insider, "I had my eyes on him the entire night, this incident did not happen!"

On November 1, Bieber's rep gave The Insider this statement: "While we haven't yet seen THE LAWSUIT, it's sad that someone would fabricate malicious, defamatory AND demonstrably false claims. We WILL VIGOROUSLY PURSUE all available legal remedies to DEFEND AND protect Justin against THESE ALLEGATIONS."

Watch more of Mariah's candid interview Monday night on The Insider.