Lindsay Lohan told talk show host Ellen DeGeneres that she was stunned by her breakup with DJ Samantha Ronson.
"Lindsay Lohan is so dumb. Her idea of getting sworn in is cursing at the judge," Rivers wrote on Twitter, People reported.
Lion-hearted Ronson Tweeted back a furious response. "Hey, Joan Rivers, you have collagen older than Lindsay."
Ronson has been creeping in and out of the "Mean Girls" star's pad as she counts down her days until incarceration. The last time the mercurial pair appeared in the news together, Lohan claimed Ronson threw a drink at her in an L.A. club.
Regardless of their past spatting, Ronson stood shoulder-to-shoulder with Lohan on Twitter.
The aging gossip monger Rivers took another 140-word swype at Lohan: "I was just reading about the new Lindsay Lohan diet, which is all liquid. 80 proof."
Samantha Ronson shot back, "Pick on someone your own age, oh wait I guess people that old can't hear."
Lindsay, who is slated to play pioneering pornstar Linda Lovelace after she gets out of jail, Tweeted on Saturday, "thank you ;)"