She grew up in Ketchum, Idaho, and attended Ernest Hemingway Elementary School. She later moved to California and lived in the Westlake Village. She attended Oaks Christian High School for two and a half years and then dropped out to pursue her modelling career. She was presented as a debutante at the Bal des débutantes in Paris, France in 2003.

In March 2009, she debuted at the fall/winter 09–10 catwalk show for Givenchy in Paris. In June 2009, she walked in the Calvin Klein resort show in New York. In September 2009, she opened the Topshop spring/summer 2010 show in London.

In January 2010, she became the new face of the Gianfranco Ferré advertising campaign. Later that year, she fronted a new advertising campaign for the Salvatore Ferragamo perfume Attimo.

In January 2014, Hemingway was the first significant Instagram plug for a crochet bikini created in Brazil but claimed by a Turkish entrepreneur and branded as a “kiini”.

In 2017, Hemingway appeared in Michelle Morgan’s It Happened in L.A., which premiered at the 2017 Sundance Film Festival, as well as Russell Harbaugh’s Love After Love, which premiered at the 2017 Tribeca Film Festival.

In 2018, Hemingway appeared in public and on Instagram having removed most of her hair in a buzz cut. She said the experience helped her find her femininity.