[1][3][4] Lilly graduated from W. J. Mouat Secondary School in Abbotsford, British Columbia, with a 4.3 GPA; she was captain of the soccer team and vice president of the student council.

[5] In university, she was a waitress, did "oil-changes and grease-jobs on big rig trucks", and was a flight attendant for Royal Airlines to pay for her tuition.

[8] Lilly's acting career began when she was discovered by a Ford Modelling Agency agent while passing the time in Kelowna, British Columbia.

She eventually called and the agency landed her several roles in commercials and non-speaking parts in the TV shows Smallville and Kingdom Hospital.

[13] The secrecy campaign meant auditioning actors could not see the full script, could read only short scenes, and knew only the basic premise of people surviving a plane crash on a tropical island.

[19][20] Robert Bianco of USA Today praised Lilly's performance in the episode named "Eggtown", saying it was almost worthy of a Primetime Emmy Award for Outstanding Lead Actress in a Drama Series nomination.

[21] After shooting the final episode of Lost, Lilly said she was considering taking a break from acting to focus on her charity and humanitarian efforts.

[34] In 2011, despite turning down a number of film offers, Lilly appeared as Bailey Tallet, a boxing gym owner, in Real Steel alongside Hugh Jackman.

[38][39] During promotion for the film, Lilly turned down a role in the X-Men franchise from Jackman, noting that she "wasn't into superhero movies" at the time.

[41][42] The character, which does not appear in the original book by Tolkien, was created by Peter Jackson and Fran Walsh as the head of the Elven guard.

[57] That same year, Lilly was set to star in a film titled Happy Place alongside Ike Barinholtz.

[65][66] That same month, it was announced that Lilly would voice a character in the English version of the animated historic epic Israeli film, Legend of Destruction, which was originally released in 2021 in Hebrew.

"[69] After gaining recognition for her role as Kate Austen in Lost, Lilly began to appear in the media and was regularly included in "Most Beautiful" lists.

[74] Lilly's roles in The Hobbit film series and the Marvel Cinematic Universe as Tauriel and Hope van Dyne / Wasp respectively, have received critical acclaim.

[22] In 2009, Lilly auctioned off custom lingerie in support of Task Brasil, "a non-profit organization dedicated to helping the lost street children of Brazil by providing them secure housing".

[82] In 2010, she auctioned off three lunches in Vancouver, Honolulu, and Los Angeles to help widows and orphans in Rwanda, a country she has made numerous trips to as part of her charity work.

[85] On July 18, 2013, Lilly debuted her book series, titled The Squickerwonkers at San Diego Comic-Con centered around a young girl who joins a group of characters described as a "family" who are all "strange outcasts" and have "very particular vices".

[102] On 16 March 2020, Lilly received mixed responses when she refused to self-quarantine during the COVID-19 pandemic, said it was "business as usual" on Instagram, and claimed that she values "freedom over [her] life".

[104] On 27 January 2022, she posted a photo on Instagram showing that she had taken part in a march against COVID-19 vaccine mandates in Washington, D.C., and said that "nobody should ever be forced to inject their body with anything, against their will".

[105][106] On 18 February, amidst the Canada convoy protest against federal COVID-19 mandates, she urged Canadian Prime Minister Justin Trudeau to meet with the protestors.