In the novel, Astrid’s age at the time of her mother’s incarceration is not quite 14 and her age at the story’s end is 19, which was, as Wells describes, "a distance we knew we could not plausibly travel with a single actress." The filmmakers dismissed the option of using two actresses because that would require a time jump that would disrupt the narrative flow, so they abbreviated the age span to take Astrid from 15 to 18 and committed themselves to finding an actress who could believably make that progression.
After an exhaustive cross-country search in which the filmmakers and casting director Ellen Lewis considered nearly 400 young women, the prospects were narrowed to a series of screen tests and finally Alison Lohman, 21, was cast as Astrid. Lohman, who made her acting debut on stage in local musical theater at age 10, launched her film career in the 1999 drama The Thirteenth Floor and has gone on to appear in a number of film and television projects, including a series regular role on the Fox drama Pasadena. "She has the range and maturity as an actress to span the age range from 15 to 18 and show the emotional changes that Astrid goes through," Kosminsky says.
As Lowry points out, it was Lohman’s ability to balance Astrid’s vulnerability with her emerging strength that made the character so credible. "If she appeared too strong, the audience would feel that her survival was unquestionable," he says, "and if she appeared too weak they might think ‘she’ll never make it,’ which can be depressing to watch. What Alison managed to do was convey inner strength while struggling with the natural doubts and insecurity of a girl her age going through such adversity."
"It’s a tough job," the director notes, commenting on the demands of the role. "She is in virtually every scene, and she is captivating. She has the kind of face that draws you in to closer and closer shots as you try to explore what’s going on behind her eyes. It was important that the actress who played this part knew how to be very still because Astrid is a watcher and a listener, a girl who sits on the edge of life observing and sketching. Alison has that wonderful quality. She seemed to understand the part inherently."
Adds Wells, "She has a natural luminance."
Before there was even a script or talk of a film, Lohman had read the novel and already imagined herself in the role of Astrid. "She was someone I could admire," Lohman says. "The great thing about Astrid is that she is not a victim, regardless of what she endures. She has an inner strength and resilience that keeps her going. She refuses to wallow in her misery.
"Astrid is an artist and sees things with that perspective," continues Lohman. "She’s vulnerable and open to things, and tends to acclimate herself to each new environment. She transforms herself into what she thinks each of these foster mothers expects her to be, as she did with her real mother, adapting to their standards while trying not to lose herself completely. It takes time before she gains the confidence to be who she wants to be."