Elizabeth was born to Jarnette, a Former Dancer with the LA ballet, and David Olsen, a Mortgage broker in Los Angeles. She is well Known as the little sister of Mary-Kate Olsen and Ashley Olsen and she has an older Brother, Trent Olsen.

Her oldest Brother is named Trent Olsen, and She has two Younger half Siblings as well. The Olsens have Norwegian ancestry on their Father's side.

When she was Growing up, her Favorite Actress and role Model was Michelle Pfeiffer. She got to Meet Michelle while She Was on the set of I Am Sam (2001).