A man who sexually assaulted his cousin in her Northamptonshire home on Christmas Day was arrested after she phoned ChildLine, a court heard.
The victim, who cannot be named for legal reasons, was aged 15 when her cousin sexually assaulted her in the kitchen of the house.
Northampton Crown Court heard the girl ran upstairs into the bathroom, locked the door, and phoned ChildLine.
The ChildLine representative advised her to inform her parents what had happened and she then wrote a letter to them.
She also informed them of another sexual assault that had happened when she was even younger.
The man was then arrested and pleaded guilty to two charges of sexual activity with a child.
He was sentenced to a three-year community order, including participation in the sexual offenders programme.
He must also complete 150 hours of unpaid work.
The ChildLine number is 0800 1111, lines are open 24/7.