She is the daughter of deceased actor Harald Heide-Steen Jr. She is best known for voicing Twilight Sparkle in "My Little Pony: Friendship is Magic". She also voices Angie in "Violetta" on Disney Channel. She joined the voice cast in Tale of the Brave. In 2015, Tiril, along with Trond Teigen, Mari Maurstad, and Terje Strømdahl, was interviewed by the Norwegian newspaper "VG" about the criticism Thomas and Friends gets. She states that she finds the statements ridiculous, and that Thomas is not one of the "bad guys" when it comes to children's television.