Breckenridge was born in Darien, Connecticut, moved to California when she was 12. She started performing in local theatre productions during her early teen years, and appeared on several television series, including Dawson's Creek, Buffy the Vampire Slayer, Freaks and Geeks, Undeclared and Charmed.

She also had the lead role in the unsuccessful UPN pilot Mystery Girl. Breckenridge has appeared in numerous films, including an uncredited role in the film Orange County and a minor appearance as Frankie Muniz's older sister at the beginning of Big Fat Liar, both of which were released in 2002. Her scene in the movie The Jacket did not make the final edit.

She had a major role playing Amy in the original short film D.E.B.S., and played Michele in the made-for-television prequel, Romy and Michele: In the Beginning (2005). Her biggest film role to date is in the comedy She's the Man, starring Amanda Bynes and released in March 2006, and she continues to voice characters on Family Guy. She currently has a recurring role in the TV-cable series Dirt playing the ambitious, but naive, tabloid magazine intern Willa McPherson.