She said she did not go to the police sooner was because she was "afraid".
"The simple reason being I blamed myself," she added. "I thought the blame would come back on me."
Donnelly, from Drumaroad Hill in Castlewellan, was curate at St Matthew's Church in Bryson Street, Belfast, at the time and denies six counts of indecent assault and one of gross indecency alleged to have occurred on dates between 31 July 1983 and 1 August 1987 when his alleged victim was aged between 10 and 14-years-old.
Giving her testimony over a live TV link, his alleged victim said the offences occurred in the parochial house of St Matthews in east Belfast.
Lapses
Defence QC John Orr suggested to her that none of the abuse had ever happened.
"Whatever the number of them (incidents), whatever age you were I want to suggest to you that nothing of that nature happened at the hands of Father Donnelly," said the lawyer.
The woman told the court: "I'm sorry, he done it. You are wrong."
Mr Orr put to her that she could not remember details such as what she was wearing, the time of day or year of various incidents but she asked rhetorically: "Would you be able to tell the time 30 years ago?"
Although she agreed that memory lapses over time "works both ways," she told the lawyer "but Father Donnelly knows he done it".
"You may well have been abused," said Mr Orr, "but I suggest it most certainly was not at the hands of Father Donnelly."
"It was at the hands of Father Donnnelly and Father Donnelly knows that," the witness replied, adding that she had nothing to gain by telling lies.
"I'm here to try to clear my head and get my life back on track, to try to get closure for this, that's what I'm here for," she told the jury.
The trial continues.