The 79-year-old star called RiRi an "idiot" after watching her open up about ex Chris Brown to Oprah Winfrey.
Soon after, E!'s Fashion Police presenter took to her Twitter account and posted: "Rihanna confessed to Oprah Winfrey that she still loves Chris Brown. Idiot! Now it's my turn to slap her."
Rihanna quickly responded: "Wow, you really do get slow when you're old, huh?"
But it appears she has since deleted the tweet. E!Online reports that Rihanna later wrote: ""Slap on some diapers," and chose to stick with that reply.
'I truly love him'
In the interview on Oprah's Next Chapter , Rihanna said she still has feelings for her ex, even after he was arrested for physically assaulting her in February 2009.
"We love each other and we probably always will, and that's not anything that we're going to try to change," she confessed to Oprah during the interview.
"I think he was the love of my life. He was my first love and I see that he loved me the same way. I truly love him. The main thing for me is he's at peace. I'm not at peace if he's not happy or he's still lonely. I care. It actually matters that he finds that peace."
Joan took to her Twitter account again soon after to express some advice for RiRi, before inviting her to appear on her own show.
She warned: "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!"