Molly Sims has come a long way from Murray, Kentucky, home to the Fiddle Festival and Lumberjack Challenge. Not that she shows it. Hanging out in a low-key Manhattan café called Friend of a Farmer, she laughs about wrecking a three-wheeler in her grandmother's backyard, professes her love for red-velvet cake, and describes herself as being "loyal as shit" to pals.

Dressed simply in a soft-gray cardigan with jeans, flats, and braided silver bangles, Sims, 36, says she's grateful for her small-town roots. "You can call it hickville or Kentucky Fried Chicken land, but to me, it was a great place to grow up," she says, ignoring the stares of male customers around the café. "My parents started a business from our basement for, like, $5, selling books. I learned so much from them." She cries a little as she describes her mother's recovery from a scary seven-hour heart surgery earlier in the week. "My mom," she says with a slight Midwestern lilt, "is my best friend."

Sims, who swapped her pre-law studies at Vanderbilt University for a career in modeling, is best known for donning a dinky, $30 million diamond bikini for Sports Illustrated, and later for playing a casino honcho on the NBC drama Las Vegas. Now she's a jewelry designer with her own line, Grayce, and also an advocate for a slew of causes, including United Against Malaria, a group with a very specific goal: obliterating malaria deaths by the year 2015.

"There are some shitty things about being a celeb—you can become slightly paranoid, slightly vain. But the good thing is, you can go to other countries, get access to all kinds of people, and bring their message back," says Sims, adding that every 30 seconds, a child dies from malaria, a disease that's preventable with things like mosquito nets, bug sprays, and simple treatments.

Sims, who has crisscrossed the globe in support of her causes, plans to travel next to South Africa, which will host soccer's World Cup in June. More than 90 percent of malaria deaths occur in Africa, and 85 percent of those deaths are children. "I always ask kids, 'What do you dream?'" says Sims. "They dream of starting families, or owning businesses, like making paper flowers." What does Sims dream? "I dream about getting married, having a family," she says. "I dream about everything—you know, good things, bad things. But I dream, and that's the point, isn't it?"

You can buy a $10 mosquito net for a mother and child at unitedagainstmalaria.org.

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