Question: Name the 2010 American biographical sports drama film directed by David O. Russell, starring Erica McDermott as Cindy 'Tar' Eklund, the lead character's sister?
Sentence (from "Erica McDermott"): Erica McDermott (born April 26, 1973) is an American actress, best known for her role as Cindy "Tar" Eklund, the lead's character's sister, in David O. Russell's film "The Fighter" (2010).
Relevant evidence: Yes