Primarily a film Actress, Hillingsø made her debut in the farce Huller i suppen in 1988, playing a small role alongside the comic duo John and Aage (Povl Erik Carstensen and Morten Lorentzen). After appearing in En verden til forskel (1989), she began as a stage Actress, appearing at the Århus Theatre from 1990-94.
In 1996, Hillingsø appeared in Peter Thorsboe's drama, Krystalbarnet in which she starred with Mirosław Baka, Grażyna Barszczewska and Helene Egelund. In 1999 she starred in Søren Kragh-Jacobsen's Mifune's Last Song alongside Iben Hjejle, Anders Hove, Sofie Gråbøl and Paprika Steen. In 2007 she appeared in Karlas kabale, based on the 2003 book of the same title written by Renée Simonsen. Also in 2007 she starred in the Danish television police drama, Anna Pihl.
