Poppa Joe won't be happy to hear this!
Multiple impeccable sources reveal exclusively to PerezHilton.com that a very nasty altercation went down between Ashlee Simpson and Michelle Trachtenberg at the 'DJ Hero' party at LA's Wiltern Theater on Monday night.
Several insiders tell us that an out-of-control Simpson verbally attacked Trachtenberg and had to be restrained.
The party-planner made a major faux pas by sitting Pete Wentz and wife Assslee directly in front of his ex-girlfriend, Trachtenberg, who attended the soiree, where Jay-Z and Eminem performed, with her new boyfriend.
Surprisingly, "The evening started off very civilly," an eyewitness tells us. "Pete and Ashlee had a pleasant conversation with Michelle and her boyfriend for close to 20 minutes." Simpson even showed Trachtenberg some baby pictures of her little boy, Bronx.
Then, the boozing happened! And more!
"Ashlee got very very drunk," an insider reveals. "She also kept making frequent bathroom trips."
Maybe she was just going to the bar a lot?
She's a new mom!
"As the evening went on and Ashlee started to get sloppier, things got out of control," one stunned partygoer tells us.
The crescendo of the night occurred when an increasingly loud and obnoxious Simpson began to give Wentz a lap dance. "She was staring directly at Michelle and starting hurling insults at her," a source tells us. "She was grinding up on Pete like a stripper. It was actually pretty disgusting!"
Clearly out of control, Asslee screamed at Michelle, "I hope you know, the whole time you were dating Pete, I was fucking him!"
Wow. Real classy!
Trachtenberg's response? She took the high road. "I've never said bad things about you. I'm happy for you guys," said Michelle to Ass.
As Simpson proceeded to get louder and in Trachtenberg's face, Mark Hoppus's wife had to drag Asslee away to avoid her physically assaulting Michelle, we're told.
"Pete looked mortified," an eyewitness tells us.
He should have been!
He should have also stood up and kept his wife in check!
[Images via WENN.]