This designer bootstrapped her way to building a cool-girl fashion brand

Nili Lotan’s Tribeca flagship has been a fixture in the neighborhood for 20 years. It’s an austere space that brings her aesthetic universe to life, one that blends silk slip dresses with military-inspired jackets, and crisp button-down shirts with utilitarian pants.

But now, across the street, there’s a second store devoted to just one thing: denim. No knits. No tailoring. Just jeans.

Denim has always been at the heart of Lotan’s collections, but Lotan has found that the...