She was a working model and the classes, held on site at the agency, were aimed to help with television advertisements.
At the end of the course, he put her in the advanced group.
He said she "had a knack for it".
A few weeks into the course, he told her he was prepared to "go out of his way" to help her work on her confidence and offered her free one-on-one classes.
"I think I must have offered him payment at some point and he said, no don't worry about it. You're special," she told the court.
The woman said she felt "quite privileged" because it was a "big thing" for someone like him to give up his time for someone.
"I felt very flattered."
He allegedly told her to keep the classes secret and she assumed it was because she was special and didn't want to "flaunt it" in front of the others.
However, the classes escalated during a "Push/Pull" exercise - which another woman has also given evidence about - and at one point he grabbed her and pecked her on the mouth.
She pushed him away, she said.
When she told him she felt uncomfortable, the man said they were "making good progress" and over the next few weeks, flattered her and showered her with praise.
"I remember him saying I was going to be New Zealand's next Charlize Theron."
At another session, the man allegedly pulled her in and put his hand under her top, over her bra. Again she pushed him away in the context of the exercise, she said.
He later pulled her in and put his hand between her legs, over her jeans before she pushed him away.
The woman remembered telling him it made her feel very uncomfortable and told him: "I'm not sure it's something I'm okay with."
That was the last class the woman attended after distancing herself from the man and making excuses.
But it was only when her actor uncle asked why she stopped the classes she told him what happened.
"He got really, really upset by that, really angry. And that's when I realised something wasn't okay [about what happened]."
She spoke with her friend - another complainant - and they decided to approach the agency's management with what happened to them.
The agency's directors said they could either go to the police or could handle it internally with the man's contract being terminated.
They were assured he would never be in a position of authority again, the woman said.
But when another complainant, the first woman to give evidence, contacted them through Facebook, they decided to go to police.
Earlier today, the court heard from the first woman who alleged the man made her kiss his penis and on another occasion pulled down her jeans and performed oral sex on her for a few seconds.
The pair later had a brief affair but it ended when the woman was told of the other women.
The defence says the sexual assaults never happened and the women conspired together with their stories.
The trial continues.
