Insecure The holly hot celebrity Ashlee Simpson caught in catfight with Pete Wentz's ex

On Monday night at Los Angeles' Wiltern Theatre, the mum-of-one went out-of-control and loudly trash-mouthed "Gossip Girl" actress Michelle Trachtenberg, according to PerezHilton.com.

Ashlee, apparently, had to be restrained at the event.

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The whole furore started when Wentz and Simpson were seated near Trachtenberg, who dated Wentz before Simpson met the Fall Out Boy bassist, reports The New York Post.

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But then Simpson started drinking.

"Things got out of control," an insider was quoted.

Following the booze session, Simpson began to give Wentz a lap dance while staring directly at Michelle.

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"She was grinding up on Pete like a stripper. It was actually pretty disgusting," a witness told the Web site.

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The heated situation came to an end when Simpson screamed at a confused Trachtenberg, "I hope you know, the whole time you were dating Pete, I was bleeping him!"

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Trachtenberg's spokesperson didn't comment on the incident. But Simpson's rep said, "It was just a misunderstanding. Ashlee has since apologized to Michelle and they remain on good terms."