Rihanna’s reunion with Chris Brown at this year’s Grammy Awards stirred up plenty of buzz among fans, but it turns out that some of the couple’s famous friends aren’t so hot about their rekindled romance either.Katy Perry, who got close with the "Stay” singer at last year’s Grammys, "doesn’t approve” of Rihanna’s decision to get back together with Brown, 23, and their friendship has suffered as a result of it, sources tell Us Weekly."They aren’t tight anymore because Katy doesn’t approve of Rihanna dating Chris Brown,” an insider said. Perry, 28, instead spent the evening on the arm of her beau, a maroon suit-wearing John Mayer, 35. The couple had a front-row view of the night’s performances, while Rihanna and Brown cuddled up elsewhere in the audience.Rihanna, 24, and Brown continued their love-fest after the ceremony as well, sipping on cocktails and "getting very affectionate” whispering in each other’s ears throughout the night at the Zing Vodka Post Grammy Party held at Hollywood’s Supperclub, an observer told Us.Us Weekly