Before starring on Lost (2004), Lilly worked a variety of other jobs. She apparently worked as a flight attendant, waitress, milked cattle, and completed oil changes on big rigs. To fund her university education, she modeled although she never considered herself a model. She appeared on G4’s Judgment Day and in an uncredited role in the 2003 film Freddy vs. Jason as a high-school girl leaning against a locker, and some appearances in a few episodes of Smallville as an extra. She had a guest appearance on the ABC supernatural horror series Kingdom Hospital (2004). She also appeared on a Live Links chat line commercial. Lilly’s first speaking role, however, was on Lost. She studied acting at The Yaletown Actors Lab with writer, director David Palffy and was first discovered by agent Jeff Palffy, formerly of Ford Models, now with PMG Management in Vancouver, who was instrumental in her first break on Lost.
When Lilly was cast as Kate in Lost, her main concern was acquiring a work visa to enter the United States. With production literally days away and no news about the visa, casting directors were forced to grudgingly begin re-casting the role of Kate. After nearly 20 auditions, Lilly’s work visa was approved/cleared but she arrived on set a day late.
Her salary in 2004 for Lost was $80,000 per episode. On the heels of her role in Lost, she was voted one of the Breakout Stars of 2004 by Entertainment Weekly and on December 14, 2006, was nominated for a Golden Globe for Best Lead Actress-Drama. Action figures of Lilly’s Lost character were released during the holiday season of 2006. On May 11, 2010, Lilly announced on The View that she places writing and being a mother as top priorities, but she likes acting as a day job and she will continue acting when possible.
Lilly is planning to write children’s books called The Squickerwonkers.
On June 19th 2011, it was announced that Lilly would play the role of the Elf Tauriel in Peter Jackson’s upcoming two-part adaptation of J.R.R. Tolkien’s “The Hobbit”, due for release in December 2012 and 2013 and currently in production in New Zealand.