Thomas Carlisle pleaded guilty to nine counts of indecent assault against Amy Alexander at Belfast Crown Court on Monday.
She was just 11 when the abuse started.
Amy was in foster care with her younger sister Natalie when she put her trust in Carlisle, a Christian man viewed as a pillar of the community.
"We had a normal family life and it was great," the 23-year-old said.
"Growing up we were taken away for birthdays and at Christmas, he would preach in church and take me along with him.
He was a good father figure and to people on the outside it was a good Christian household
However, when Amy's mother died, she was formally adopted and the abuse began.
She continued: "Once social services stopped their involvement that was when the abuse started. My mum had passed away by this stage too.
"I would have recognised the sound of the door handle in my bedroom going down and I knew that was him coming in, or I would hear his footsteps on the stairs.
"Whenever he did what he did I was only 11 - I felt uncomfortable with what he was doing but I didn't know if it was right or if it was wrong".
Amy finally broke her silence at the age of 19 and now, four years on, justice has been done.
Carlisle confessed to abusing her and was sentenced to a year in jail and three on probation upon release.
The 62-year-old is now banned from working with children and will be on the sex offenders register for 10 years.
Amy said: "I'll never forget what I went through with the abuse but now that he is in prison I can put a lot behind me and live a happier life."
A spokesperson for the Northern Trust said it will review the information brought to light in the court case.
"Mr Carlisle was assessed and approved as an adoptive carer. The Trust will review all of the information it holds in respect of this case and thoroughly investigate its role in the assessment of Mr and Mrs Carlisle and the support and care of Amy and Natalie".