Armstrong was born in Tokyo, Japan to a Scottish father, Hunter Armstrong, and an Italian mother, Sylvia. Her mother designs spas for resorts and her father teaches soldiers close combat training. Her first name, pronounced [sɑmɪːrɑ] or Sa-mee-rah is Gaelic. The first 3 months of her life her parents pronounced her name Sam-air, until they met a Gaelic man who told them it was properly pronounced Sa-mee-rah. She lived in Japan for several years, before moving to Hawaii and later Sedona, Arizona where she grew up. They've also lived in Malaysia and China.  attended the University of Arizona, but dropped out because of the school drama department's policy of barring freshmen from involvement in productions. Her brother, Hunter Armstrong, is currently attending the University of Arizona. After her departure from school, she moved to Los Angeles. She is now dating Kevin Banek. Her first major break into film acting was as one half of the conjoined twins the Fratelli sisters in the parody movie Not Another Teen Movie. Armstrong also had a recurring role on Freaks and Geeks, and had guest appearances on Judging Amy, Party of Five, C.S.I.: Miami, Numb3rs and the The X-Files. She was romantically linked to actor Aaron Paul. Armstrong appeared in The O.C. for one episode, and was brought back at fan request for several episodes of the first season. She had a recurring role on the HBO Television Series Entourage. Her most recent film projects include Stay Alive, Just My Luck and Rise. Armstrong has been cast in the drama Dirty Sexy Money, which was picked up for the 2007-2008 television season by ABC. She will play a character named Juliet Darling. When not acting, Armstrong is often designing clothes for her own clothing brand called NARU. She has also appeared in music videos such as in Hanson's "Penny and Me" and Daniel Powter's "Bad Day".