She told investigators the man touched her bum "quite a lot", her upper thigh twice and her breasts about three times.
On one occasion she feared he would rape her, the girl said.
"I asked for a back massage and then he started rubbing down by my bum and I felt like scared because I didn't ask him to rub down there," she said.
On another occasion, she said the man put his hands under her clothes, near her genitalia.
"I was wearing shorts and he rubbed . . . up and down my thigh and I felt really uncomfortable."
The girl also told police she had disclosed details of the alleged abuse to someone close to her.
That person told her the defendant was probably just "being nice", she said.
But Mr Fairley said the defence would be calling them as a witness and they would say no such disclosure of indecent acts had been made.
The allegations emerged in 2014 when the teenager told her father what had happened.
Mr Fairley asked why it had taken so long for her to come forward with her version of events.
"I didn't actually know it was this serious. I didn't know it was going to end up like this," she said. "I didn't know that was the right thing to do."
Mr Fairley suggested the only massage that had taken place was a single foot rub but the girl firmly rejected that.
Earlier, the defence lawyer produced a string of photos - taken during the period of the alleged offending - which he suggested showed the pair looking "very comfortable together".
On one occasion a photo showed the teenager on the defendant's back.
The girl explained the defendant would have invited her to do so but Mr Fairley was sceptical.
"You're just making that up. You voluntarily got on his back. How do you say this man's been sexually abusing you?" he said. "You look pretty comfortable there, don't you? Your private parts against his back."
"You jumped on his back because there was no sexual abuse," the lawyer said.
"There was sexual abuse," the girl replied.
The other complainant will give evidence tomorrow.