Sofia Richie Flashes Underboob for 'Billboard,' Dishes on Her 'Special Relationship' With Justin Bieber

Sofia Richie is quickly becoming Hollywood's 'It' girl.

The fresh 18-year-old (she just celebrated her birthday on Aug. 24!) is all grown up, flashing her abs and major underboob in a white mesh crop top and matching pants on the cover of Billboard magazine's style issue. In her accompanying interview, the daughter of Lionel Richie and sister of Nicole Richie gets candid on growing up in the spotlight, finding her own style and, of course, Justin Bieber.

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Sofia and Justin first sparked romance rumors last month when they were spotted holding hands on a beach in Laguna Beach, California, and enjoying a morning hike in Los Angeles. It wasn't long before the two became Instagram official, and began documenting their adventures as they headed to Japan together as part of the 22-year-old pop star's Purpose World Tour.

"We have a special relationship," Sofia gushes. "Justin is very easy to talk to, and that's hard to find with people in Los Angeles."

Once Justin started posting pics of the blond beauty, fans (and a few of his exes!) began leaving negative comments, criticizing their relationship and hating on Sofia. It ultimately led the "Sorry" singer to delete his Instagram account, but Sofia says she remains unbothered -- thanks to growing up with her famous sister.

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"I remember the paparazzi and the s**t people would say to Nicole, and she wouldn't respond," she explains. "I'm going to be real with you -- It. Doesn't. Bother. Me. As long as I'm happy."

Sofia says that Nicole -- a fashionista and reality star who rose to fame by starring in The Simple Life with Paris Hilton -- has taught her a lot about confidence, owning who you are and discovering your own personal style.

"My sister is a big part of my actual style," Sofia, who has made a few cameos on her sister's VH1 reality show, Candidly Nicole, dishes. "Our style is not similar whatsoever, but she helped me find myself and find what I really liked."

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While Sofia loves going glam in front of the camera, her everyday style is much more laid-back.

"I like just jeans and a T-shirt, with some high-tops," she tells Billboard in a behind-the-scenes video from her cover shoot. "I'm very simple, I'm edgy. Put together but, honestly, I love guys' clothing. I will go crazy in the guys' section with the hoodies."

Sofia began modeling in 2014, and has already appeared in a number of fashion magazine editorials, including Elle, Vanity Fair Italia, Vogue China, Nylon, Lady Gunn, Unleash'd, ES and Who What Wear. She was also the face of Madonna's Material Girl fall 2015 collection.

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"Madonna influenced me a lot," she says. "She's all about really being yourself, and not giving a care in the world, and I really take after that."

"I love modeling because I get to see everything that inspires me. Then I go home and sketch," Sofia continues, adding that it's her dream to debut her own ready-to-wear collection of "trenches, high-waisted pants, pantsuits [and] silks."

And with two fashionistas in the family, you can guarantee Lionel gets a lot of heat for what he wears.

"For an event, my dad's very picky, same stylist forever, no one's telling him what to wear," Sofia explains. "Sometimes he'll be leaving the house looking a little crazy, and I'll have to tell him to go change, but besides that, I don't really give him much advice."

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