Zara Phythian - who appeared in Doctor Strange with Benedict Cumberbatch - is accused of numerous sexual offences along with her husband Victor Marke.
The girl, who is now an adult, told police that the couple filmed most of the abuse in an attempt to recreate pornographic scenes.
Mr Marke, 59, and Ms Phythian, 36, deny all of the offences.
A police interview with the woman was played to jurors at Nottingham Crown Court where she described details of the alleged sexual offences between 2005 and 2008, when the girl was aged between 13 and 15, and before the couple were married.
The couple were both martial arts instructors in Nottinghamshire at the time, and the woman told police she had looked up to Ms Phythian because of her martial arts success.
She said the first offences happened after the couple gave her alcohol to drink, and Ms Phythian dared her to give Mr Marke oral sex. She said Mr Marke then had sex with both of them.
"I knew it was wrong but I just didn't know how to get out of the situation or say anything," she told police.
"I remember trying to copy Zara's reaction at the time because I looked up to her and tried to be like her in every way."
As the abuse continued, she said Mr Marke threatened to smash her kneecaps if she told anyone.
"He just said nobody would believe me if I told them anyway," she told police.
"They always had a power over me."
Mr Marke and Ms Phythian - whose legal name is now Zara Marke - are jointly accused of 14 charges of sexual activity with a child in relation to the woman.
Ms Phythian would have been 20 or 21 years old when the alleged abuse started, and Mr Marke would have been 42 or 43.
Mr Marke is also accused of four additional charges of indecently assaulting a child, which are in relation to another woman who complained to police.
She was aged 15 when she was allegedly abused by Mr Marke, between 2002 and 2003.
The court was told that Mr Marke was married to a woman called Juliet when the abuse started.
However, the marriage broke down, the court heard, after Mr Marke had an affair with Ms Phythian, who was a teenager herself at the time.
The trial continues.
Photo source BBC Caption: Actress Zara Phythian