Joan Rivers is known to put her foot in her mouth, and Kristen Stewart was far from thrilled when she took a jab at her personal life. Almost two years ago, the "Twilight" star was caught kissing her married "Snow White and the Huntsman" director, Rupert Sanders, while she was dating Robert Pattinson. Rivers used this as comedic material, and Stewart threatened to sue!

"Many stars only do one thing well," Rivers wrote in her new memoir "Diary of a Mad Diva."

 "Of course, the best one-trick pony is Kristen Stewart, who got a whole career by being able to juggle a director's balls."

Rivers told Splash News over the weekend that the "On The Road" actress threatened legal action.

"She obviously didn't read our disclaimer, which is that it's a comedy book," Rivers slammed Stewart. "I can't wait to get her into court because I want to get a puppet and I want her to show me on the puppet where she thinks I claimed she touched her director. So I am looking forward to it."

"I'm a comedian; I've been doing it for 50 years," she continues. "If people don't get it, then don't come and see me, and don't read the book. If you're going to take it seriously, you're a fool."

According to TMZ, Stewart's lawyer contacted River's lawyer, and threatened to sue for defamation unless she rid the slutty references. Rivers insists that it's a joke and meant to be funny.

An insider believes the "Twilight" star's attorney might have backed down.

This is hardly the worst thing Rivers ever joked about. We told you in April the comedienne was under fire for joking about the Cleveland kidnapping victims.

Rivers made a tasteless comparison between her daughter Melissa's guest room and the victims' living conditions during hostage.

"Those women in the basement in Cleveland had more room," she teased.

When TMZ questioned her on the matter she put her foot in her mouth once again, stating "they got to live rent free for over a decade."

Do you think Stewart needs to lighten up, or is Rivers out of line? Let us know your thoughts in the comments section below.