She lived and worked on the family's grain farm with her three sisters—Trina, Tammy, and Tara. She was discovered at age 17 by a modeling agency scout while standing in line at a local movie theatre.
Helfer retired from fashion modelling in and claimed all her shoots since then are related to projects or product endorsements. In , she played "Eva" in the independent film White Rush. In , she portrayed Farrah Fawcett in the telefilm Behind the Camera: The Unauthorized Story of Charlie's Angels.
When Chelsea finds out that her friend is recovering from a breakup, she says she should do so at Charlie's house. The project was written and produced by Ronald D. Moore and directed by Michael Rymer.
Helfer played the role of Number Six , a humanoid Cylon operative. She continued that role as a regular cast member in the TV series , which completed its fourth and final season on March 20, Due to the special nature of the Number Six character — there are many "copies" of Number Six with distinct personalities — Helfer has, in effect, played numerous roles on the series.
In , she reprised her role as Number Six in Battlestar Galactica: The Plan — a television movie that tells the story of the series from the Cylons' point of view. In , she voiced a prototype Cylon in the prequel Battlestar Galactica: She appears as herself in Old 97's music video for their song, "Dance with Me".
She made a guest appearance in the pilot episode of Fox's mid-season series Human Target. Tiberium Wars , Veronica Dare in Halo 3: Wings of Liberty as well as the expansion sets Starcraft II: Heart of the Swarm and Starcraft II: Legacy of the Void. Web of Shadows and Ultimate Spider-Man. The show was cancelled in November because of its very low ratings. She guest starred in the second season of the Jane Espenson scripted romantic comedy web series, Husbands. In , she appeared in the series finale of Falling Skies as the Espheni Queen, the leader of the alien race that had invaded Earth and devastated humanity.
She also played Louise, a woman attending a doll convention, in the web series Con Man. In , Helfer was added to the main cast for Season 2 of the Fox TV series Lucifer , playing the lead character's mother who is also the exiled wife of God.