Firth was encouraged by her mother to try out modeling, after watching an episode of “The Model Agency”, which featured a documentary about the Premier Model Management. Her mother called up the agency and arranged a meeting with them. After attending an open-call casting, Firth was signed on the spot.
Beginning her modeling career at age 17, Firth soon began modeling internationally: She gave her runway-debut at the New York Fashion Week SS2012 for Odilon. She gained attention from the fashion industry after walking in the SS2014 Prada menswear show and starring in the Prada-fall 2013 campaign, which also featured Christy Turlington, Catherine McNeil, Cameron Russell, Freja Beha Erichsen, Fei Fei Sun and Rachel Williams and was shot by Steven Meisel. With this feat, she became the first black model in 19 years to score a Prada campaign. The last black model to book a Prada campaign was Naomi Campbell for the fall 1994 campaign. — Source