"Both of them are seen frequently holding. Cassandra seems to be IRL and has some good drags but the scene often cuts away before the exhale. Kestie may not be IRL and is seen holding more than smoking. Both of them have a scene where they exhale, with Cassandra having a couple more."
Other references to this movie:
Kestie Morassi - Picture - holding, Wolf Creek (2005), 43k
, Allposters.com