Byrne began her acting career in 2005 in the short film CryBaby, before portraying Chloe Daniels in an episode of the British TV drama Doctors, though she had previously auditioned for the role of Luna Lovegood in Harry Potter and the Order of the Phoenix.
In 2009 Byrne earned the role of Pansy Parkinson in the sixth film in the popular Harry Potter series, Harry Potter and the Half-Blood Prince, before reprising her role in the final two films of the series. Following the end of the Harry Potter series, she then played Brittany in Lake Placid: The Final Chapter, as well as appearing in several short videos written by fellow Harry Potter star Jessie Cave for her website Pindippy.
During 2013, Byrne played the role of Sarah in the short film Lashes. She also played the role of Lisa in the action-thriller film Skybound, alongside Gavin Stenhouse. Byrne became a regular cast member for the fourth season of the sci-fi show Falling Skies. She moved to Vancouver for the filming of Falling Skies.
- Day One of Twenty-Two Thousand, Give or Take
- Never Let Me Go
- I Carry Your Heart With Me
- Live Through This
- Best Served Cold
- Hold Me, Thrill Me, Kiss Me, Kill Me
- Cold as Ice
- Postcards from the Edge
- This Woman's Work
- Moonlight on the Bayou
- I Would for You
- Days of Future Past
|2008||Doctors||Chloe Daniels||Episode: "Kiss My Asp"|
|2009||Harry Potter and the Half-Blood Prince||Pansy Parkinson||Supporting role|
|2010||Harry Potter and the Deathly Hallows: Part 1||Pansy Parkinson||Cameo|
|2011||Harry Potter and the Deathly Hallows: Part 2||Pansy Parkinson||Supporting role|
|2012||Lake Placid: The Final Chapter||Brittany||Supporting role|
|2014-present||Falling Skies||Alexis "Lexi" Glass-Mason||Season 4-present|
|2015||Sorority Murder||Jennifer Taylor||Post-production|
|2015-present||The Vampire Diaries||Nora||Season 7; recurring role|