Stavros Niarchos, Paris Hilton Party in South Beach

They split in May, reconnected temporarily in July, broke up at some point in the early fall and got back together again sometime in late October.

It's hard to keep track of Paris Hilton and Stavros Niarchos, but the two sure seemed like an item at the Miami nightclub Ink on Friday night.

Hilton and Niarchos met up around 1 a.m. with Hilton's pal Brandon Davis and sister Nicky Hilton (who earlier hit Andy Roddick's charity celebrity poker tournament at Hard Rock Live), but only had eyes for each other when the DJ played Billy Idol's "Mony Mony" and Hilton treated the Greek God of Poontang shipping heir to a lap dance.

The group later moved on to the club Mokai in Miami Beach, where Niarchos joined Hilton on the dance floor, at one point even lifting her up and spinning her around on his shoulder.

Their night hit a snag at around 3:15, when the pair stepped outside and briefly argued about their plans (Niarchos wanted to leave but Hilton didn't. Plus the barefoot heiress had left her panties shoes inside the club). But Stavros Niarchos apparently won out.

So what's the story with Niarchos and Hilton, who was recently photographed with a diamond on her ring finger? Her rep says unequivocally:

"Paris is not engaged. She does wear rings on different hands and fingers and depending on what's comfortable, but she is not engaged."

Still, a source close to Hilton says that "Not only are Paris and Stavros together, but they are in love."