She has multiple credits for Hallmark, starting with her first role in Hallmark Hall of Fame's Promise (1986), with James Garner and James Woods. Among other appearances, there are A Carol Christmas (2003), Wedding Daze (2004), Back to You and Me (2005), Mystery Woman: Wild West Mystery (2006), McBride: Semper Fi (2007), and Moonlight & Mistletoe (2008). In 2013, Niven was cast in Hallmark Channel's first original drama series Cedar Cove, opposite Andie MacDowell and Bruce Boxleitner. Niven is currently appearing in the series Chesapeake Shores with Treat Williams and Diane Ladd. For Hallmark Movies & Mysteries, she has been cast in the Murder, She Baked and Crossword Mysteries movies.