Gerry Adams' niece did not reveal the extent of the sexual abuse she suffered at the hands of her father, Adam's brother, because she wanted to spare her mother's feelings, she told the court.
Aine Adams, 40, has accused her father Liam Adams of sexually abusing her between 1977 and 1983, when she was between four and ten years old.
During the trial, which began in Belfast this week, Aine Adams said that when she first reported the abuse in 1987, she did not tell police about specific incidents, including a rape allegedly carried out while her mother was giving birth. She retracted the allegations later that year.
"I have never told mummy the details of what happened. It would be hard for any mother – they are giving birth, and their husband is raping their daughter. As a 13-year-old, I thought I was doing the right thing," Ms Adams told the court, according to the HeraldScotland.com.
Liam Adams, the 57-year-old brother of the Sinn Fein president, had denied the 10 counts of child sex abuse including rape, indecent assault and gross indecency.