She is best known as Nurse Ellen Crozier in the New Zealand television series Shortland Street to which she was nominated for Best Actress at the 1998 TV Guide Television Awards. She is also known as Cheryl West in Outrageous Fortune. Her film credits include films such as: Absent Without Leave (as Betty), The Last Tattoo, and Perfect Strangers (as Aileen).
Malcolm is the co-founder of the New Zealand Actors' Company.
She has two sons with her former husband Allan.