The woman was the final complainant of seven to give evidence at the trial of Sr Mary Theresa Grogan, formerly known as Sr Peter.
She told Sligo Circuit Court that the nun indecently assaulted her as an eight-year-old more than 35 years ago. A second woman also made similar claims in court yesterday.
The final complainant, a 47-year-old who is now the mother of a 17-year-old girl, told the court yesterday "it all came back" when she heard Sr Grogan's voice in 2006 in a shop in the town where the school is located.
The trial had already heard from five other women, saying the 63-year-old nun put her hand inside their underwear and petted their bottom. Some said she also moved her hand round to touch their vagina.
The court has also been told the nun was just out of teacher training college when the alleged offences were committed in a primary school in the Midlands.
Sr Grogan, of the Mercy Order, has denied 63 counts of indecent assault against seven women when they were seven and eight-year-olds.
The court was told she was principal of the school for a period in the 1980s while she was still known as Sr Peter.
She changed to Sr Mary Theresa Grogan when she joined the missions in Zambia in 1990.
The prosecution case is expected to end today and the defence will start next week.
The case was moved from the Midlands town where the alleged offences happened to Sligo at the defence's request.