2. Rihanna + Katy Perry: There were rumors that the ladies fell out when RiRi rih-united with Chris Brown. Perry allegedly did not approve of the rebooted relationship, which petered out as quickly as it restarted. These lovely ladies haven't been seen hanging out and bro'ing like they used to, leading us to wonder if the rumors of strain and tension are real. Oh, and remember, RiRi skipped Perry's 2010 nuptials to Russell Brand to finish some work on an album. Friends don't do that, since they can jetset. RiRi could have chartered a private plane to the wedding in India and have been back to work the next morning.