The 24-year-old singer broke down when she accepted that she still loves her ex-boyfriend Chris Brown who was accused of physically assaulting her in 2009, reported Sun Online.
Rivers expressed her disagreement over the issue on Twitter.
"Rihanna confessed to Oprah Winfrey that she still loves Chris Brown. Idiot! Now it's my turn to slap her," she tweeted.
This irked Rihanna and she replied on Twitter saying, "Joan Rivers wow - u really do get slow when you're old huh? Slap on some diapers."
