On May 1, Hilton, in a brunette wig, shopped at the Grove in Los Angeles with Leinart, 22, a 6'5" Heisman Trophy-winning quarterback recently drafted by the Arizona Cardinals. That night, PEOPLE reports in its new issue, Hilton and Leinart were spotted together at L.A. club Shag. "They seemed really into each other," says one witness. "He was very touchy-feely."
Leinart's rep denies that they're dating, and Hilton's publicist, Elliot Mintz, says, "She knows Matt, she likes Matt. They are friends. I don't want to go any further than that. They have known each other a while."
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But don't feel too bad for Niarchos. On April 27 – days before Hilton's flirtation with Leinart – he was spotted partying with Lindsay Lohan. Three days later, he dropped by her hotel. Says a source close to Lohan, "(Stavros) has been calling her all the time."
Paris & Stavros: Their Final Days
Monday, April 17
Hilton hosts a 21st-birthday bash for Niarchos and 100 friends at her Beverly Hills home. (She held additional parties for her beau in Las Vegas on April 21 and April 22.)
Thursday, April 27
Paris flies to Austria. That night, Niarchos is spotted with Lohan outside a private party in Beverly Hills.
Sunday, April 30
While Hilton parties at Austrian nightclub Pascia, Niarchos visits Lohan at the Chateau Marmont, where she's staying during her Just My Luck press tour.
Monday, May 1
Paris flies back to L.A. and hangs out with Leinart. The two then hit L.A.'s Shag, where Niarchos spots them.
Tuesday, May 2
At 3:30 a.m., Niarchos and Hilton get into a screaming match at her gate. She doesn't want to let him in. He won't leave – and winds up sprawled on the ground. (He finally hops in a cab at 9 a.m.) Hilton's rep confirms the split later that day.