Britney Spears had the BEST sleepover with the Kardashians! Kim Kardashian was first to spill the beans about the friend reunion on Friday when she posted photos of the pop star at her Hidden Hills home in California with the singer's longtime manager, Cade Hudson, and her sister Khloé. Kim and Brit have been pals for years, but this marked their first public get-together in 13 years! Incredible! Related: Britney Spears Tells Kevin Federline To Eff Right Off In New Post! Well, it looks like the Circus singer had an absolute blast! She gave fans another look into the slumber party on Saturday...