What Does a Cool Girl Look Like?

The store aims to capture the same qualities of Khaite’s clothing: sleek, self-assured, a little gothic-romantic. And, in spite of Ms. Holstein’s protests, cool.

Building a Mystery

“Have you ever seen ‘Friends With Money’?” Ms. Holstein asked. Her film references run deep. She was sitting on a black leather sofa, overseeing fittings for her runway show. “Frances McDormand plays this luxury fashion designer — she has a very expensive fashion line at Barneys — who stops showering and only wears her pajamas everywhere. She’s not descending into madness or anything, she just stops caring. I always joke that I feel like that’s me now. I love clothes and I love shopping, but everything has to be very easy.”

Ms. Holstein wears little makeup. She parts her smooth chestnut hair down the center, pushed behind her shoulders like an afterthought. She dresses casually, too: a Khaite sweater or cardigan, thick and soft, over loose pants. Although her recent preference for elastic waistbands is more related to her being, at time of this writing, nine months pregnant.

She was drawn to fashion from a young age, when she would copy fashion sketching templates belonging to her older sister. She dressed boyishly as a child, emulating her brothers, yet “had infatuations with really feminine girls in my class, who dressed really frilly.”

As she got older, she’d steal luxury designer pieces from her mother’s wardrobe and gradually acquired her own: a Dior bag for graduation, a beloved Nicolas Ghesquière-era Balenciaga leather jacket for Christmas in her 20s. Her father worked in finance, and the family moved from Connecticut to San Diego to London, where she spent most of her youth, then back to California just before Ms. Holstein finished high school.

She came to New York to attend Parsons, where, during her junior year, she designed a collection of six sailor dresses. After Teen Vogue spotted the dresses at events around the city, the magazine brought her in to show the collection to editors. One editor tipped off Barneys, which placed an order. Ms. Holstein dropped out of school to start her namesake label.