While struggling financially, she landed her first role as the title character in the web-based video series Rachel's Room in 2001.She went on to earn a Young Artist Award nomination in 2002 with her portrayal of 15-year-old murder victim Martha Moxley in the television movie Murder in Greenwich.
In 2004, Grace was cast as Shannon Rutherford in the television series Lost, on which she was a main cast member for the first two seasons, winning a Screen Actors Guild Award shared with the ensemble cast.
Leaving the series, Grace was keen to work more prominently in film having starred opposite Tom Welling in The Fog in 2005.
Grace reprised the role of Shannon in two more episodes of Lost, including the series finale.
In Los Angeles, Grace and her mother moved around often as they struggled financially, taking out short-term rents rather than paying for permanent residence while eating a basic diet, as it was all they could afford. I landed a few bit parts; nothing substantial, but LA taught me to grow up ...
She appeared in Suburban Girl, The Jane Austen Book Club (both 2007), and Taken (2008).