Rihanna in Twitter Feud With ... Joan Rivers Plus, she's moved on ... to Rob Kardashian? By Evann Gastaldo, Newser Staff Posted Aug 27, 2012 10:06 AM CDT 9 comments Comments This April 24, 2012 file photo shows singer Rihanna attending the TIME 100 gala, celebrating the 100 most influential people in the world, at the Frederick P. Rose Hall in New York. (AP Photo/Evan Agostini, file) (Newser) – Joan Rivers likes to pick fights on Twitter, and this time she's engaged Rihanna. Rivers called Rihanna an "idiot" and said she wanted to "slap her" after the singer told Oprah Winfrey she still loves Chris Brown. Rihanna's first response, which she ultimately deleted: "wow u really do get slow when you're old huh?" Later, she tweeted "Slap on some diapers." (That one remains up, E! reports.) Rivers was unfazed, replying, "Honey, @Rihanna, everyone knows: If he hit you once, he'll hit you again. Read the statistics." She ended with an invitation—one we have to imagine will be ignored—for Rihanna to appear on Fashion Police. Rivers may be happy to hear that Rihanna has apparently moved on: The Daily Mail reports that she was spotted Saturday night going go-karting with ... Rob Kardashian.