NEW YORK — Britt Robertson is no stranger to having to emote on the screen. She played a foster kid who finds her birth parents in the CW series “Life Unexpected” and a young waitress kidnapped and held hostage in CBS’ “Under the Dome.”

The 27-year-old actress is now starring in the Netflix comedy “Girlboss,” based on the rags-to-riches story of Sophia Amoruso, who started selling vintage clothing on eBay in her early 20s and built the Nasty Gal empire that made her a millionaire. The best-selling “(hash)Girlboss,” published in 2014, is the basis for the series.

Robertson says she thought acting in a half-hour comedy would be easy, but playing a version of the fearless and witty Amoruso, called Sophia Marlowe on the show, was “energy-sucking.”

“It took more out of me than anything else I’ve ever done in my life, in a good way. You want to be challenged. You want to be fulfilled and that takes energy, but … it’s hard,” she said recently.

Robertson had to change her look for the show, dying her blond hair to chestnut brown and adding bangs. She also rocked vintage clothing to represent Amoruso’s style.

“I think it was really important for me to change the way I look. Even when we were doing the costume fittings we would have to put a wig on me. It was so hard to picture the real Sophia character I was trying to embody while I look like a bleach-blond surfer girl. “

Amoruso stepped down as CEO of Nasty Gal in 2015. The company filed for Chapter 11 bankruptcy the following year.