planned to dance and sing the night away
, but made sunning the day away her priority beforehand Saturday in Las Vegas.
With her concert just hours away, the former American Idol judge
spent the day basking in the sun and munching on finger foods at MGM Grand's Wet Republic. Joining her in relaxation: boyfriend Casper Smart
Smart sat by Lopez's side
, stroking her hair and resting his hand on her knee as she laid by the pool in a two-piece midriff-baring white ensemble by Bec & Bridge.
As the day wore on, Smart shed his shirt and jumped in the pool, while Lopez basked in the sun – relaxing several bungalows away from where Prince Harry was hanging out
Following her concert at Mandalay Bay, Lopez and Smart headed to Pure Nightclub. Arriving after 1 a.m., the duo headed straight to the VIP stage as Lopez's music played overhead and video screens showed her music videos.
Lopez was seen twirling an illuminated foam glow stick while Smart danced in front of her.
An onlooker told PEOPLE, "They seemed really comfortable."