After a day of shopping on Saturday, the "Scream & Shout" singer dined at Meatball Spot at Town Square with manager Larry Rudolph and two other people – and was later joined by boyfriend David Lucado and six more friends.
Wearing an orange crop top and leopard print Christian Louboutin stilettos, Spears enjoyed classic meatball sliders with mozzarella cheese and homemade mac and cheese, created by Top Chef star Carla Pellegrino.
Spears and Lucado "seemed happy, sitting across from each other and chatting for most of the meal," an onlooker tells PEOPLE.
For dessert, Spears ordered a Bananas Foster ice cream sandwich and sampled a birthday cake milkshake.
Once their meal was finished, the camera-shy couple exited the restaurant through the kitchen just in time to catch Shania Twain's "Still the One" show at Caesars Palace.
OK here is one and only one image of Britney Spears at Meatball Spot this afternoon. I got a great one of her hair ;) twitter.com/ThomasShue/sta…— Thomas Shue (@ThomasShue) March 24, 2013
– Mark Gray and Melody Chiu