Acker was born in Dallas, Texas, to Robert Acker, a lawyer, and Sandra Bruyere, a housewife of French ancestry. Acker studied ballet, modern dance, and jazz dance for 13 years. In her junior year of college, Acker enjoyed a short stint of modeling work for the J. Crew clothing catalog. In 2005, she joined the cast of Alias for its final season, playing the villainous Kelly Peyton. Acker guest starred on fellow Buffyverse actress Alyson Hannigan's new show How I Met Your Mother, in which she was reunited with Angel co-star Alexis Denisof (Hannigan's real-life husband), who has a recurring role on the show.