By Sophfronia Scott
July 16, 2001 12:00 PM

Shoshanna Lonstein is used to attracting unwanted attention. Long before she ever met Jerry Seinfeld, Lonstein coped with the not-so-delicate effects of having a bosom that blossomed at an early age. “When I was 13, grown women would make horrible comments because their husbands had looked at me,” she recalls. “People would stare at me on the beach.”

It was that scrutiny—rather than the media blitzkrieg launched when the 18-year-old Lonstein became the significant other of the then-39-year-old comedian—that prompted her current incarnation: designer of the Shoshanna clothing line, flirty dresses and sexy swimwear emphasizing looks for well-endowed women. “As soon as I heard she was doing bathing suits I thought, ‘Wow, they’re going to be yummy!’ ” says Cosmopolitan editor-in-chief Kate White. “She’s always been conscious that women couldn’t get a perfect fit.”

Now the 26-year-old Lonstein is filling the niche—and thousands of cups sized A to DD—quite nicely. Launched in 1998, the brand last year raked in more than $6 million in sales nationwide. Julia Roberts wore her rose-print corset in Erin Brockovich. And Kristin Davis has donned Shoshanna dresses on Sex and the City. “There’s something elegant about the clothes,” explains Kal Ruttenstein, a senior vice president at Bloomingdale’s. “They’re sexy and sweet at the same time.”

Lonstein admits her well-publicized romance with Seinfeld may have opened some doors. “Obviously I received more attention than most people would have starting out,” she says. “But it wasn’t so much positive attention. It’s human nature to want to see people fail, and that was terrifying to me.”

But failure, it seems, wasn’t written in Lonstein’s stars. Born on Manhattan’s affluent Upper East Side to Zach, 57, chairman of a computer company, and Betty, 54, an ex-ballerina (brother David, a real estate developer, is 23), Lonstein attended all-girls’ schools that inspired her take-charge attitude.

Soon after graduating from Nightingale-Bamford School in 1993, she met Seinfeld in Central Park. The following year a smitten Lonstein transferred out of Washington, D.C.’s George Washington University and moved into her own digs in Los Angeles to be near the star. But it wasn’t the happily-ever-after she had hoped for. Enrolled in classes at UCLA during the day, she spent most nights eating pizza at home alone. “I was dating someone who worked seven days a week, 24 hours a day,” she says. “That wasn’t his fault, but we were at different points in our lives.” The couple split nearly three years later.

Back in New York after graduating in 1997, Lonstein decided to give fashion design a shot. To learn the trade, she worked sans salary at a lingerie manufacturing plant. Her father eventually kicked in funds, which Lonstein used to make her first samples. “She’s a very hard worker,” says dad Zach. “At 6 a.m. she’s answering her e-mails.”

He should know. Lonstein still lives in the family’s 14-room Fifth Avenue abode. But she may soon leave the nest, for the weekends anyway. She recently purchased a four-bedroom beach house in the Hamptons. And though the press has linked her romantically to Ben Affleck, Lonstein says she is unattached “for the first time in my life.” Not that there’s anything wrong with that. “Work is my boyfriend. I focused so much on it and took care of it,” she says. “Now it’s starting to take care of me a little.”

Sophfronia Scott

Natasha Stoynoff in New York City