WWW- Troubled actress Natasha Lyonne went from Hollywood golden girl to a volatile slob in a downward spiral that eventually landed her in jail, said her former friend and landlord.

The "American Pie" star was being sought yesterday on a warrant after she failed to show for a court hearing Monday to face charges of harassment, criminal mischief and trespassing.

"She really was one of the smartest, most insightful people I have ever known," said actor Michael Rapaport, who met the 26-year-old Lyonne in 1997 and later invited her to rent an apartment in the building he owns on E. 18th St.

"It remained very peaceful until the fall of 2003," he said in an article he wrote for next month's Jane magazine.

Then he started receiving complaints from other tenants. "Reports kept coming in," said Rapaport, whose films include "Small Time Crooks" and "Hitch."

"People were going in and out of the apartment, [one of the tenants] was telling me about the late-night parties, and 'random dudes sprawled out on her sofa at all times. [Another tenant] had a little dinner party. Natasha was screaming up at them throughout the party."

Things got so bad, he said, he travelled from his Los Angeles home to confront her. He was shocked by how much she had changed.

"I felt sick to my stomach the moment she touched me," he said. "Her body was so skinny."

The complaints continued until Dec. 17 when Lyonne allegedly barged into her neighbor's apartment, tore mirrors off the wall, threatened to sexually molest a dog - and was arrested.

Rapaport evicted her - then went to inspect her apartment.

"It looked like a grenade had gone off," he said. "There was garbage everywhere. There were glasses smashed in the kitchen and standing water in the clogged tub with flies hovering over it. "That girl needs help."

A representative for Lyonne was not immediately reachable.