"Jen is insulted that Courteney took the initiative and went straight up to Brad when he was there with Angelina," disclosed an insider.

"In Jen's mind, Courteney could have easily avoided them. It's like Courteney went out of her way to be super nice to Brad."

The "Babel" star gave Courteney a bear hug and cooed, "Hello, sweetheart. It is so great to see you."

And he introduced Arquette and Cox to Angelina as "dear friends."

Meanwhile, Aniston will have to get over her anger for a steamy kiss with her pal.

Jennifer Aniston didn't have to kiss up to BFF Courteney Cox for a guest role on her FX drama Dirt. But she does have to kiss.

In the FX drama Dirt March 27 episode, Aniston gives Cox's tabloid editor Lucy Spiller a "goodbye peck," a source close to the show tells PEOPLE. It's not the full-on makeout session "But, yes, it's on the lips."

Dirt producer Matthew Carnahan confirmed to USA Today that Aniston will play a lesbian on the show.

Aniston will play Tina Harrod, a fellow magazine editor and bitter rival to Cox's character, Cox.