My Sister's Keeper (2009)

Elle Fanning will play Anna, the girl who sues her parents for medical emancipation, while Dakota will take on the role of Anna's sick older sister Kate. Cameron Diaz is playing their mother. According to Variety, "The girls are younger than they were in [Jodi] Picoult's novel, but a decision was made to cast them younger because it was age-appropriate for Diaz.