Britney Spears celebrated a very happy long birthday weekend with boyfriend Jason Trawick during a romantic trip to Puerto Vallarta, Mexico.

"When they landed, she got to the [private] villa and was blown away," a source tells our friends over @PEOPLE of the couple, who arrived on Dec. 2, Spears's 29th birthday. "Jason had arranged a red velvet cake for her birthday."

Last week, Spears's camp denied a tabloid report that Trawick "beat on" the pop star. And their intimate getaway, which included a private chef and a fridge stocked with fresh fruit, seemed to prove their point.

"They suntanned and did a lot of relaxing and decompressing," says the source. "They seemed very much in love. "

Indeed, a source close to Spears told our friends over @PEOPLE last week that "the couple's relationship is better [than ever]. Britney and Jason lately have been very happy together."