Lohan, 19, and Niarchos, 21, were spotted kissing on May 15 at the Manhattan nightclub Butter. The next evening, they partied together at Bungalow 8 until 3 a.m., and on May 17 they caught an Elefant concert at Webster Hall before meeting friends at Bungalow 8 once again.
Although sources confirm the two are hooking up, Lohan was also spotted smooching British singer Jamie Burke on May 7 and hanging out at clubs with X-Men: The Last Stand director Brett Ratner in April.
As for Hilton, she seemed unfazed at the Cannes Film Festival on May 20 as she danced and sang Rod Stewart's "Do You Think I'm Sexy" atop a table at a party hosted by Suite Miami.
