Hallier got her start in the 1981 cult classic horror film My Bloody Valentine. Hallier followed up her success with guest appearances on 1980s television series such as The Dukes of Hazzard, Trapper John, M.D., and Simon & Simon.
In 1986, Hallier co-starred with Harvey Keitel in the thriller Blindside, and in 1989 she appeared as Yvette on the popular soap opera Days of Our Lives, following this role with a recurring role as Shannon Pressman on the daytime drama Santa Barbara in 1990. In 1996, Hallier appeared in the horror film Night of the Twisters. After appearing in the television movies Leona Helmsley: The Queen of Mean and A Woman Scorned: The Betty Broderick Story, Hallier would become associated with supernatural and science fiction through her work on series such as Star Trek: Voyager and Poltergeist: The Legacy in 1997.
In 2000, she portrayed Joanna Lanier in the television series In a Heartbeat. In 2002, Hallier was cast in the film My Name Is Tanino. The following year, she starred in the popular Canadian program Strange Days at Blake Holsey High.