It was the hospital chaplain, a Catholic priest. He went to jail for it, many years later, like so many of his colleagues in Ireland, but only after decades of misery for Ms Collins.
''I never connected his abuse with the church,'' she says. ''I thought it was somehow my fault and that I was a bad person who had brought it on myself. I had years of depression and agoraphobia that included nine admissions to psychiatric wards.''
As a young adult, anxious that other children not be hurt as she had, she told a priest in her parish. ''He told me it was probably my fault, that I must have led the poor man on, but that I was forgiven and I could go away and forget about it.''
Ms Collins did go away, into more years of silence and depression. The misery did not lift until after her attacker, Father Paul McGennis, was jailed in 1997 over offences involving her and another child he abused 18 years after Collins. He was later convicted of having raped a third girl, 24 years after he attacked Ms Collins.
She has no doubt the validation given to her by those court cases, and the findings of four inquiries into child abuse, helped her to recover. She says of the opening up of Ireland's cesspit of secrets: ''I think it's helped everybody, really, except the Catholic Church … It's certainly worked for survivors. Even as late as the 1990s, it was difficult for any survivor to be heard or believed in any way. That's not the case any more.''
Australia's royal commission into child sex abuse, announced last week by the Prime Minister, Julia Gillard, will look at the Catholic Church and other institutions.
In Ireland, the church has been the focus of inquiries because its traditional reach there incorporated almost all schools, hospitals, orphanages, charities and welfare organisations.
And it is the church hierarchy that has time and again been found guilty of covering up scandals and protecting perpetrators.
''The revelation that had the biggest impact was not that the church had abusers,'' Ms Collins says. ''It was news of the systemic cover-ups that angered people.''
In her case, the bishop to whom she took her story told her the priest concerned had no complaints against him: ''But they had known 30 years earlier he was an abuser. A few months after he abused me, the church found out he was doing it. He used to take indecent pictures of the children and he sent them to the UK for processing, and Kodak … picked out a roll and sent them to police here. The police commissioner did not investigate, but brought the pictures to the archbishop. They took him out of the hospital and put him in a parish.''
Ireland's Prime Minister, Enda Kenny, a practising Catholic, was so outraged by stories such as this that after a damning report last year, he launched an attack on the Vatican that made world headlines.
The Cloyne inquiry found a 1997 letter from the Vatican criticising a new policy by the Irish church hierarchy of reporting all offenders to police. The Cloyne report documented, as had three other inquiries before it, patterns of clerical deceit.
Breaking with decades of subservience to the church by Irish politicians of all stripes, Kenny stood up in Ireland's parliament and attacked Rome.
He said the report exposed an attempt ''to frustrate an inquiry in a sovereign, democratic republic - as little as three years ago, not three decades ago. And in doing so, the report excavates the dysfunction, disconnection, elitism … the narcissism that dominate the culture of the Vatican. The rape and torture of children was downplayed or 'managed' to uphold, instead, the primacy of the institution, its power, standing and reputation.''
Rome removed its ambassador to Ireland, and Dublin closed its embassy to the Vatican.
Ireland has since reinforced its determination to act on secular principles of child protection by making it mandatory to report sexual abuse.
Meanwhile, ordinary Catholics have voted with their feet. While national attendance at weekly Mass is about 45 per cent, in Dublin the figure is less than 20 per cent - both a huge drop from the 90 per cent attendance of 30 years ago.
Dublin's Archbishop, Diarmuid Martin, said in February: ''The fact thousands of children were abused within the church … is a scar the church will bear for generations.''
Of the Murphy report into the misdeeds of the Dublin Archdiocese before his time, he said: ''I offer to each and every survivor my apology, my sorrow and my shame for what happened to them … the Archdiocese of Dublin failed to recognise the theft of childhood.''
The church has set up new structures to deal with abuse. Andrew Fagan, director of child safeguarding for the Dublin Archdiocese, says the new system reports all complaints to police immediately.
Church volunteers are trained to be abuse-aware and develop practices that involve careful supervision of children.
But Marie Collins feels she can no longer be part of the church. She still believes in God but has found herself slamming into what she believes is a wall of resistance in the church to change on child abuse.
In February, she went to Rome for a Vatican seminar on child abuse for bishops, where she met a church official who gave her hope because he was passionate about the need to tackle the problem.
Soon afterwards, he was demoted.