The daughter of American author Danielle Steel, Traina grew up in San Francisco before moving to Malibu to attend Pepperdine University. Early in her career she interned for Carine Roitfeld at Vogue Paris and subsequently moved to New York where she assisted stylist Marie Amelie Sauve. Traina has modelled for brands including Louis Vuitton and became a Chanel beauty ambassador in 2009.
Traina is executive creative director of Assembled Brands, the holding company founded in 2013 by Adam Pritzker to develop emerging fashion designers. In 2014, the company launched e-commerce venture, The Line, followed by The Apartment by The Line, a New York showroom in which lifestyle products curated by Traina are laid out as if in a private home. A second Apartment is located in Los Angeles, while the brand also hosted pop ups in Chicago and The Hamptons. The Line launched carrying brands such as Acne, Tabitha and their own ready-to-wear in-house brand, Protagonist. In 2015, the brand expanded into homeware with their Tenfold line, and a second ready-to-wear line, Khaite, debuted in 2016.
Traina is also a creative consultant and has worked with clients including Balenciaga, Altuzarra and Erdem. In 2018, Traina collaborated with the luxury face oil company Rodin Olio Lusso on a capsule collection of limited edition lipsticks and lip and cheek oils. The collection marked The Line's expansion into the beauty sector, in line with the company raising $100 million from the asset management firm, Oaktree Capital to expand its product categories.