Harper, who was diagnosed with terminal brain cancer five months ago, joined the production of "The Town That Came A-Courtin'," a made-for-TV movie that will air on UP cable network and began shooting in Vancouver Wednesday.
The movie is based on Ronda Rich's novel of the same name, and stars Lauren Holly, Cameron Bancroft and Lucie Guest.
Harper will play Charlotte, a bed-and-breakfast owner in the fictional town of Bliss.
In welcoming the "always inspirational" Harper to the cast, UP described the movie as an "uplifting romance."
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