Vassilieva was born on October 22, 1992, in Minneapolis, Minnesota, in Hennepin County Medical Center,[1] the only child of Russian immigrants.

[5] Less than a year later, Vassilieva received her first role, playing the granddaughter of a retired Russian general in an episode of the CBS television series The Agency.

She won a Young Artist Award in 2006 for Best Supporting Actress in a TV Drama for her role as Ariel DuBois in Medium.

Vassilieva played a terminally ill teenager, Kate Fitzgerald, in the 2009 adaptation of Jodi Picoult's novel My Sister's Keeper, directed by Nick Cassavetes.

[9] In 2011, she guest-starred on Law & Order: Special Victims Unit in the episode "True Believers" as Sarah Walsh, a piano BFA candidate who is raped in her New York City apartment.