Juliet Hulme, of Hulme-Parker murder notoriety, has spoken out about the killing, saying she and Parker were never lesbians.
Hume - who became British writer Anne Perry - and Pauline Parker murdered Pauline's mother in Christchurch in 1954 by bludgeoning her with a brick.
A film version of the story of the two 15 year olds, Heavenly Creatures, portrays the lesbian relationship between the two.
But Perry has told the London Times Saturday Magazine that although they were never lesbians the relationship was obsessive.
The schoolgirls lured Mrs Parker to Victoria Park in Christchurch, on June 22, 1954, where they hit her repeatedly on the head with half a brick in a sock.
Pauline planned the "moider" in her dairy. The girls wanted Mrs Parker killed so that Pauline would be sent to live with Juliet/Anne Perry.
The subsequent trial became one of the sensations of the time. The court was shocked with Pauline's diary. An entry for June 22 was headed: The Day of the Happy Event.
The girls were jailed separately -- they never saw each other again -- and given new identities on release.
Perry said of her part in the killing that she "made a profoundly wrong decision.
She added that she feared Pauline would take her own life "and it would be my fault."
She also says doctors tried experimental -- now known to be mood-altering -- drugs as part of her treatment for tuberculosis in a Christchurch sanatorium.
" A long needle in your behind every third morning. They'd catch you when you were still asleep."
Perry became the only child inmate in Mt Eden women's prison in Auckland.
She said she spent the first three months in solitary where she got down on her knees, cried and repented.
"I was guilty and it was the right place for me to be."
During the day we did hard labour but I collapsed after two weeks and then I started sewing uniforms.
"The woman who kept that sewing room took a fondness for me; she wrote to me until she died.
She was in Mt Eden for five and a half years.
Perry said the prison was raw and brutal -- no fruit and no library.
"I memorised the few books I had; screeds of the stuff. In prison we got little time alone except the nights -- nights were a great blessing, not having to share a room. And when the light goes out and there's nothing, then the light goes on inside your head."
Perry was released aged 21 and was put on a flight to Rome to be met by her father and taken to England.
She travelled and worked in a variety of jobs from air hostess to insurance underwriter.
She also attracted many boyfriends, but not daring to know anyone well enough to explain about her past.
"I do know what it's like to feel like an outsider."
Perry, now 67, is a prolific crime writer of more than 50 novels.
She lives with her brother, a retired doctor who is now her full-time researcher, in a stone barn -- restored with some of the royalties from the 20 million books she has sold -- in Portmanhomack on the east coast of Scotland.
She is also involved with the Mormon community after converting to the church 35 years ago.
"I like its doctrine that you have to keep learning and that no one is excluded, no one is penalised.
Parker became a riding instructor in Kent living under the name of Hilary Nathan.