She and boyfriend Jason Trawick flew in Thursday to partake in the weekend wedding festivities of her assistant and close friend Brett Miller.
They bunked down in an oceanfront room at the Newport Beachside Hotel where members and friends of the wedding party were staying, a source tells PEOPLE, but she didn't make it to the kickoff event.
"During Thursday night's rehearsal dinner, Britney ditched the reception and ordered room service for herself, Jason and her bodyguard," the source tells PEOPLE. "They had spaghetti bolognese, turkey burgers, chicken noodle soup, a fruit plate and one turkey sandwich."
Leaving her parents and friends at the Sunny Isles hotel Friday, Spears and Trawick moved into the Frank Sinatra Suite at the Fontainebleau in Miami beach because the Newport hotel's "pool wasn't private" enough.
Their new digs were reportedly a $35 million penthouse that rents for $15,000 a night, is four bedrooms, has a kitchen, whirlpool, piano and a large balcony overlooking the ocean.
After a few hours shopping, Spears and Trawick headed back to the Newport for another wedding party. "At one point, during the early evening Jason took Britney's hand and twirled her to a cool Frank Sinatra sound," the source tells PEOPLE. "It was cute and romantic."
The couple left the party after Spears noticed that a group of kids spotted her in the ladies room, and headed for the Fontainebleau club LIV.
"Britney and Jason were dancing and laughing and having a great time at LIV," another source tells PEOPLE. "He was very sweet and affectionate with her. And she got very excited when her favorite songs came on."
Miller's wedding took place Saturday at Miami's Spanish Monastery where she married her sweetheart, Frank Lionetti.