Oh snap! Ashlee Simpson has been left shamefaced after getting into a drunken war of words with the former girlfriend of husband Pete Wentz.

According to a scoop from CelebrityRoyale.com, the drama started when Pete and Ashlee ran into Michelle Trachtenberg at the DJ Hero party at LA’s Wiltern Theater on Monday night. Michelle and her new man sat directly in front of Pete and wife Ashlee. The two couples pleasantly chatted and things were fine — and then there was a turn.

“Pete and Ashlee had a pleasant conversation with Michelle and her boyfriend for close to 20 minutes,” says a champagne-poppin’ spywitness. ”Ashlee got very very drunk and she also kept making frequent bathroom trips.”

“As the evening went on and Ashlee started to get sloppier, things got out of control,” a partygoer confesses. “A loud and obnoxious Ashlee began giving her husband a lap dance. She was staring directly at Michelle and starting hurling insults at her..She was grinding up on Pete like a stripper. It was actually pretty disgusting!”

A completely wasted Ashlee screamed at Michelle, “I hope you know, the whole time you were dating Pete, I was fucking him!”

Celebrity Royale writes: “Michelle Trachtenberg was clearly not as drunk and decided to remain classy. She said, ‘I’ve never said bad things about you. I’m happy for you guys.’ Ashlee continued to get loud and got in Michelle’s face. Finally, Mark Hoppus’s wife had to drag Ashlee away from Michelle to avoid a physical assault….”

A rep for Ashlee admits that the Melrose Place star lashed out at Michelle in her drunken stupor, but adds that she has apologized: “It was just a misunderstanding,” Ashlee’s rep claims. “Ashlee has since apologized to Michelle and they remain on good terms.”