Source: Chelsea Handler freaks out trying to keep John Mayer from Jennifer Aniston and her new fiance

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It seems there’s still bad brewing between former flames Jennifer Aniston and John Mayer.

According to an eyewitness, Chelsea Handler was involved in some intense drama Thursday night before a triple date with her hotel mogul boyfriend Andre Balazs, Jennifer Aniston and fiancé actor/writer Justin Theroux, and Drew Barrymore and husband Will Kopelman at the restaurant inside West Hollywood’s chic Sunset Tower Hotel.

FOX411's Pop Tarts columns is told a restaurant staff member warned Handler that John Mayer – who dated Aniston from early 2008 through 2009 – also had a reservation for the restaurant that evening.

It was upon hearing this news that Handler went into freak-out overdrive.

“Chelsea was pacing around and seemed really stressed as she was trying to figure out what to do. A few people were staring at her because it was clear something was really wrong,” an insider told FOX411’s Pop Tarts column. “She looked kind of crazy and totally on edge.”

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A plan was apparently concocted whereby staff would lead Mayer through a different entrance and he would be seated at the back of the restaurant, far from Aniston’s sight.

“I don’t even think Jennifer knew he was there or knew there was any drama before she got there,” said our source. “And John definitely didn’t come to the table if he was there. Chelsea finally seemed to relax, and it seemed they had a nice dinner.”

Reps for the restaurant, Handler and Mayer did not respond to a request for comment. A rep for Aniston responded that they don’t give out the whereabouts of their clients.