Model Sofia Richie, the 17-year-old sister of Nicole Richie, isn't a little girl anymore, as evidenced by her impressive first appearance at New York Fashion Week.

The youngest child of singer Lionel Richie wowed as she walked the runway Thursday in a crimson Tabitha Webb gown at the American Heart Association's Go Red For Women Red Dress Collection show.

RELATED: Nicole Richie's Little Sister Sofia is a Fashionista in the Making

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Sofia Richie at NYFW.

Turns out, she was overcoming one of her biggest fears in the process: taking a tumble on the catwalk.

"I've just watched so many falling videos on YouTube that I'm petrified, especially since my dress is so long," Sofia told E! News beforehand. "They had me in platforms, but the falling theory was in my head, so I decided to choose my own shoes." She'd even previously told Elle magazine, "I don't think I could ever do runway."

Big sis Nicole, 34, is Lionel's oldest child whom he adopted with first wife Brenda Harvey. He and his second (now ex) wife went on to have two more kids of their own, Sofia and her older brother Miles Brockman Richie, 21.

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Sofia and Nicole Richie.

Sofia has said that though she's close to her older sister, Nicole is very protective of her.

"I don't feel like we'll ever be equals," she told Elle. "Nicole will always give me guidance as a big sister. She tells me every day that she's mad that I'm growing up."

Aww!