While Paris Hilton's baby brother was rotting away in a Lost Hills jail cell yesterday after a DUI arrest, La Paris was en route to Las Vegas -- where she shook her ass all night alongside Kristin Cavallari at Pure Nightclub.
As TMZ reported, Barron Hilton called big sis and pleaded with her to bail him out ... she said no. But Paris can't say "no" to a party! We know she wasn't celebrating the success of "The Hottie and the Nottie."
Paris -- Sorry Bro, I Gotta Party!
