The Pitch Perfect star is being sued by Charlotte MacInnes, the Australian lead actor of the musical comedy The Deb.
MacInnes claims she was defamed by social media posts from Wilson that suggest she is a liar who retracted a sexual harassment complaint to advance her career.
Wilson claims the young actor confided she felt uncomfortable after the film's co-producer Amanda Ghost asked her to have a shower and a bath together in September 2023.
"I took it as a sexual harassment complaint," Wilson told the Federal Court on Tuesday.
"She was confiding in me as the director of the movie."
MacInnes denies making the complaint and maintains she never said she felt uncomfortable.
She ended up sharing a bath with Ms Ghost in their swimwear after the producer suffered a medical episode but maintains she doesn't feel it was inappropriate.
Wilson revealed she had been working on The Deb for years and was weeks away from shooting when she had the conversation with MacInnes.
"This is a fun girl power movie and the worst thing that could have fallen into my lap at that point was a sexual harassment complaint," she told the court.
Wilson said she "100 per cent" asked the young actor if she was OK but couldn't remember whether she had asked if MacInnes wanted to report the complaint.
"I did the best I could. I listened to her," she said.
The Bridesmaids star said she reported the complaint to another producer on the phone, but denied the statement was a recent invention.
She also denied having any involvement in ordering or authoring the creation of websites attacking Ms Ghost that described her as the "Indian Ghislaine Maxwell" and a sex trafficker.
She said her US lawyer hired The Agency Group to assist her with a legal dispute with her co-producers, repeatedly insisting the firm had not been commissioned to work for her.
The firm is accused of creating smear websites against Hollywood actor Blake Lively on behalf of her co-star Justin Baldoni.
Wilson rejected suggestions from MacInnes' barrister Sue Chrysanthou SC that she was being utterly dishonest and pretending to misunderstand what was being asked.
"You know you've lied about this topic for a year haven't you?" Ms Chrysanthou asked.
"No," Wilson responded.
A word document containing the allegations published on the websites could have been created by anyone using the name of her company, the Hollywood star told the court.
She said she didn't think she would have been horrified by the websites' allegations against Ms Ghost because the producer had been bullying and harassing her at the time.
Wilson agreed she would describe herself as a champion of women and said there was a lot of evidence of her supporting and promoting women over her 25-year career.
She denied mistreating MacInnes and Ms Ghost while working with them on the film, labelling accusations of private and public bullying as "absolute nonsense".
"Inappropriate behaviour from a person in power to an employee is a serious problem," she said.
Wilson had smiled as she entered the courthouse flanked by security but she appeared more guarded when she got into the witness box.
Ms Chrysanthou became exasperated when questioning the actor, at one point asking her: "Are you serious?"
She claims Wilson falsely portrayed herself as a whistleblower who spoke up to protect MacInnes when she was actually using the alleged complaint as leverage in a dispute with her co-producers.
Wilson's lawyer Dauid Sibtain SC contends MacInnes changed her story to ensure her career as an actor and a musician thrived with Ms Ghost's assistance.
He has argued MacInnes' reputation hasn't suffered any harm as a result of the social media posts.
Wilson will continue giving evidence on Wednesday.
1800 RESPECT (1800 737 732)
National Sexual Abuse and Redress Support Service 1800 211 028
