The superstar singer and the Fashion Police host had a heated exchange on the social networking site Friday, after Rivers called Rihanna an "idiot" for revealing she still had feelings for ex-Chris Brown in the Next Chapter sit-down.
"Rihanna confessed to Oprah Winfrey that she still loves Chris Brown. Idiot! Now it's MY turn to slap her," Rivers tweeted.
Rihanna quickly responded, saying, "@Joan_Rivers wow u really do get slow when you're old huh?"
She later deleted that message, but wrote, "Slap on some diapers," and kept that one up.
Rivers later quipped, "Honey, @Rihanna, everyone knows: If he hit you once, he'll hit you again. Read the statistics. PS – Love to have you on Fashion Police!"
Something tells us it may be a while before the Bajan beauty takes Rivers up on that offer.