HISTORICAL NON-SENSE!!!
I've read dozens of books on Stalin and the Soviet Union and not one, NOT ONE (!!) of the historians mentions any "Australian" woman spending the night with Stalin. It simply did not happen. It's like asserting that John Kennedy spent the night of NOV 27 in a gay brothel. Ridiculous!
The boring fact is that Stalin had a stroke sometime during the night of FEB 2/3, 1953 or the morning of FEB 3. In fact, the other members of the Poliburo simply let Stalin die by withholding medical treatment for several hours (though, to be fair, the Soviet doctors lacked the medications and techniques used everyday in advanced countries to save stroke victims and mitigate the damage caused).
So, however much you may like the movie's main theme, it is NOT history in any way and I can say this with absolute confidence even though I have yet to see the movie.
One of Stalin's housekeepers was his mistress as was treated by the Politburo as Stalin's widow, but she was a Russian and NOT an Australian.
In any event, given Stalin's paranoia (which had grown to psychotic proportions by the time he died in FEB of 1953) and xenophobia, it is inconceivable that a woman from an "imperialist" nation would have found her way to Stalin's bed.
Stalin was something of a ladies' man; in fact, the suicide of his second wife, Nadia Alliluyeva is believed to have been precipitated by her discovery that Stalin was cheating on her with the wife of a Soviet official.
If you can find it, I highly reccomend the HBO film "Stalin" starring Robert Duvall. Unfortunately, not only is it out of print, it was also filmed before DVDs were available and only used VHS copies remain. While, of course, it takes liberties with history, it is probably as close to a historically accurate portrait of the "wonderful Georgian" (Lenin's nickname for Stalin in pre-Revolutionary days) on film as we're likely to see.
If you REALLY want to understand Stalin, I suggest Robert Conquest's "Stalin: Breaker of Nations." It is less than 300 pages and was written for the general reader. It provides an excellent, if short, portrayal of the worst mass-murderer in history. (And mentions nothing about Australians.)
"The greatest trick the devil ever pulled was making the world think he didn't exist."