In 1985, Lyon appeared in the Canadian miniseries
Anne of Green Gables as Prissy Andrews. The following year, she starred in an episode of
American Playhouse, "Valentine's Revenge," opposite Victor Ertmanis. She made her feature film debut as the lead in the
supernatural horror film
Hello Mary Lou: Prom Night II (1987), playing a teenager haunted (and eventually possessed) by a vengeful spirit. Lyon went on to work in television through the 1980s and 1990s, and provided voice work for multiple episodes of
Sailor Moon in 1995. She returned to film with a minor role in the drama
Focus (2001), starring
William H. Macy and
Laura Dern, followed by the independent comedy
Childstar (2004). In 2010, she appeared in three episodes of the
ABC series
Happy Town. Lyon had a minor role in the psychological thriller
Regression (2015) before appearing in
Guillermo del Toro's critically acclaimed fantasy film
The Shape of Water (2017). In 2019, Lyon had a multi-episode arc on the American political thriller series
Designated Survivor, starring
Kiefer Sutherland. ==Personal life==