“I had never thought that fashion ever applied to me, really, so having people my age to talk to and share our interpretations of it was something that I really cherished,” she said. She went on to become a blogger and was featured in Teen Vogue for her work. Later, the magazine hired her as an intern and regular contributor.

“Teen Vogue is my family,” Ms. Sicardi said. “I grew up in those hallways. I was probably at the magazine for longer than I was ever in a classroom.”

Elaine Welteroth, the print magazine’s second and final leader, had been a mentor to Ms. Sicardi. Ms. Welteroth took over from Ms. Astley in 2016 and was officially named editor in chief this spring, in a grim climate for magazines aimed at the older-teen set (R.I.P. CosmoGirl, YM, Teen People, Elle Girl).

Until recently the youngest editor in chief at Condé Nast — she is 30 — Ms. Welterorth quickly became an Instagram celebrity and received heaping praise for the magazine’s newly “woke” tone. Teen Vogue 2.0, as she reimagined it, wasn’t just about clothes and makeup; it was about news, politics and social justice, too.

In her first year, Ms. Astley had emphasized how crucial it was for her to create a product that was “racially, ethnically diverse, fashion-wise diverse. We don’t say someone is or isn’t Teen Vogue.” The magazine entered the field at a time when millennials were just beginning to document their lives online, with LiveJournal and MySpace, and the platforms that continue to replace print publications showcase diversity even more effectively.

It wasn’t until 2015, after a decade of mostly white, mostly famous cover stars, that Teen Vogue changed course, with a cover featuring three little-known black models. The issue became the year’s best seller, underscoring the appetite for fashion magazines that reflect some version of real life.