Born and raised in Dallas, Acker grew up wanting to become a ballerina. She studied ballet for several years as a child, before an unexpected knee injury permanently ended her dreams of becoming a professional. Still harboring a love of performing, it was only then that Acker turned to acting. She enrolled in the drama department at Southern Methodist University, and began performing on stage in numerous Shakespeare productions throughout Dallas, including "Much Ado About Nothing." After earning her B.F.A. from Southern Methodist, Acker moved to New York City. She landed small parts in two independently produced films, including 2001's "The Accident," before relocating to Los Angeles. Shortly after arriving in L.A., Acker won the part of Fred on "Angel," a spin-off of Joss Whedon's much-beloved "Buffy the Vampire Slayer" (The WB, 1997-2001; UPN, 2001-03). The Fred character was initially intended to arc after a few episodes, and then quickly disappear from the storyline. However, Whedon believed Acker to be such a good fit for the character that he expanded Fred's role. By the time "Angel" went off the air after five seasons in the spring of 2004, she had appeared in 70 episodes.After lending her voice to the animated action series, "Justice League" (Cartoon Network, 2001-04), Acker nabbed her next big part as the villainous Kelly Peyton on the final season of J.J. Abrams' spy-drama "Alias" (ABC, 2001-06). Over the next few years, Acker landed recurring parts on the action-packed "Drive" (Fox, 2007), Whedon's fan-favorite "Dollhouse," and the ABC kidnapping drama "Happy Town" (2010), but neither show lasted long. In 2012 Acker reteamed with Whedon for two of the writer-director's film projects, the horror-mystery "The Cabin in the Woods" and "Much Ado About Nothing," the latter of which was film entirely on location at the writer/director's house in Santa Monica. Acker had less than three weeks to prepare for her starring turn as Beatrice in the film, which received mostly positive reviews upon its limited release in late 2012. That same year, Acker appeared in a recurring role as a gifted computer hacker on the second season of the CBS crime drama, "Person of Interest," (2011-16). She joined the cast of the show at the start of the third season in the fall of 2013.