Breaking down several times in the witness box at Belfast Crown Court on Tuesday, the 20-year old woman said she embarked on a sexual relationship with McPeake - who was around 67 at the time of the alleged offences - and that the sexual activity was consensual and that she loved him.
McPeake, 72, and his family are well known in traditional Irish music circles.
He is currently standing trial on 12 counts of sexually abusing the teenager over a period spanning from June 2009 to May 2010.
The complainant alleges that sexual conduct between the two began during a music trip to the Republic in the summer of 2009 and ended when she broke it off after becoming sick of lying to her friends and family about her relationship with the pensioner.
During a second day in the witness box, the complainant told the jury how she and McPeake had sex "whenever we could" and that sexual activity took place in a minibus, in workshops, in a music school and in his car.
As she was cross examined by the musician's barrister about the allegations she made against McPeake, she repeatedly told the court she was in a relationship with him.
Each allegation she made was rejected by the barrister, who accused the woman of making the incidents up and of stalking his client.
The barrister also accused the complainant of "pretending you were in a fantasy relationship with him", to which she replied: "I was in a relationship with Francie. It wasn't a fantasy."
She was asked about several incidents she claimed happened and was also challenged about kissing McPeake in a car with her friend present.
When she was asked about being afraid of whether or not her friend could see the kiss, the woman said: "I didn't really care. I was in a bubble. My life revolved around Francie ... that was it for me."
When the trial began on Monday, a Crown prosecutor told the jury that the issue in this case wasn't one of consent, but whether or not McPeake had done the acts he is accused of.
Since he attended a police station voluntarily in December 2012, McPeake, formerly of Eliza Street Close in the Markets area of Belfast, has maintained his innocence.
In a prepared statement to police, McPeake said: "I have never done anything with this child."
He branded her allegations as "false, malicious and without foundation", claimed he and his family had suffered due to a "campaign of harassment" from her and her relatives since 2010, and added: "She is attempting to destroy my life."
The defence barrister accused the woman of threatening McPeake with suicide, of stalking him and of threatening to contact social services.
He also asked the woman about messages she had sent to members of the McPeake family on Facebook, and of telling McPeake he had wrecked her family, and she was going to "hit him where it hurts" and wreck his.
Sobbing, the woman said: "I hated him for what he had done to me. I still do. I thought he loved me and he clearly didn't.
"All I wanted was an apology for him, that's all I wanted. I wanted him to say that he was wrong, that what he did was wrong.
"Why should he have a family and a wife and why should he see his grandkids and everything else after what he put me through."
When McPeake's barrister said his client "did not sexually abuse you as you have described" both north and south of the border, she answered: "He did."
The trial is due to resume on Wednesday.