A film based on the true life story of two young women in Christchurch, New Zealand (in New Zealand ``based on the true life story'' has a much stronger meaning than in America). The house in which the events happened (and in which the film was shot) is now the staff club at the University of Canterbury It's on Ilam Road, with an entrance opposite the Students Union. At the time the father of one of the two women was a senior university officer.

From Star-Sun, 1st September, 1954:

Girls murderers' sentence - place of detention to be decided today

Girls murderers sentence place of detention to be decided. Talks today by Ministers
(From our Parliamentary reporter) Wellington August 31.
Cabinet Ministers tomorrow will discuss where Pauline Yvonne Parker and Juliet Marion Hulme, who have been convicted of murdering Parker's mother, will serve their sentences of detention. The Ministers are expected to discuss the matter after the weekly meeting of the Executive Council. The Minister most directly concerned is the Minister of Justice (Mr T. C. Webb). As Minister of External Affairs, Mr Webb will leave on Thursday for Manila to attend the talks on the proposed South-east Asian Security Organisation. Where the two girls will be detained has been exercising the minds of senior officials of the Department of Justice and the Minister since sentence was pronounced last Saturday, because it is generally held that the girls should be separated. There is only one girls' Borstal institution in the country, and the policy is against sending girls of Parker's and Hulme's age to the Mount Eden Prison.

From http://home.istar.ca/~matte/katecreature.htm:
Heavenly Creatures was Kate Winslet's first film. It is set in 1950s New Zealand, and Kate plays Juliet Hulme, the new girl in school, a British transfer to Christchurch. She is not afraid to speak her own mind, and gets in trouble by correcting her teachers publicly. Shy wallflower Pauline Rieper (Melanie Lynskey) is enraptured by this new girl in school, and the two girls immediately strike a friendship. They create a surreal medieval kingdom in an alternate universe inhabited by unicorns, butterflies, and clay people. Their respective parents suspect their friendship may be little "too" friendly, and decide that the two girls should be separated. Both girls become hysterical at the thought, and retreat further into their own little fantasy world, free from the burden and torment of reality. Juliet develops tuberculosis, around the same time that her mother (Diana Kent) and father (Clive Merrison) decide to get a divorce. Juliet is forbidden to have any visitors, and when she gets better she finds out that her parents have decided to send her off to Africa. Pauline pleads with her mother (Sarah Peirse) and father (Simon O'Connor) to go with Juliet, but to no avail. The two girls then plan actions that will have dire consequences for all involved.
From the film:
I'm going to the fourth world. It's sort of like heaven, only better, because there aren't any Christians."
sources:
http://www.kwfc.com/filmography/heavenlycreatures.shtml
http://home.istar.ca/~matte/katecreature.htm
http://www.domusaurea.org/borovnia/places.html
http://www.ccc.govt.nz/Library/Heritage/ParkerHulme/