Sofia Vladimirovna Vassilieva (born October 22, 1992; Russian: София Владимировнa Васильева) is an American actress. She is best known for playing the children's book heroine Eloise, in two made-for-television movies, Ariel Dubois in the Emmy-winning TV series Medium, and the cancer patient Kate Fitzgerald in the 2009 film adaptation of My Sister's Keeper by Jodi Picoult.
Vassilieva was born in Minneapolis, Minnesota, the daughter of Russian immigrant parents Drs. Larissa Vassilieva and Vladimir Vassiliev, a biologist and physicist respectively, both from Novosibirsk