I'd write my name on everything." She also appeared in the independent film The Safety of Objects (2001), as the tomboy daughter of a troubled single mother (Patricia Clarkson).Stewart also played a tomboy, diabetic daughter of a divorced mother (Jodie Foster) in the film Panic Room (2002).Her character is immobilized during most of the film.The next year, she played the character Maya in Fierce People (2006), directed by Griffin Dunne.
In 2015, she received critical acclaim for her role opposite Juliette Binoche in Olivier Assayas's French film Clouds of Sils Maria, for which she won the César Award for Best Supporting Actress.
Stewart starred in the Lifetime/Showtime television film Speak (2004), based on the novel by the same name by Laurie Halse Anderson.
Stewart, 13 at the time of filming, played a high school freshman, Melinda Sordino, who nearly stops speaking after being raped.
For her portrayal of Tracy – a teenage singer who has a crush on young adventurer Christopher Mc Candless (played by Emile Hirsch) – Stewart received mixed reviews.
While considered her work a "sturdy, sensitive performance", and the Chicago Tribune noted that she did "vividly well with a sketch of a role", Variety The film received Screen Actors Guild nomination for Outstanding Performance by a Cast in a Motion Picture.