The Pitch Perfect star is being sued by Charlotte MacInnes, the lead actor in the musical comedy The Deb, which Wilson directed, co-produced and starred in.
MacInnes claims she was defamed by the older actor in social media posts that suggested she is a liar and a sellout who withdrew a sexual harassment complaint to advance her career.
The posts alleged MacInnes confided to Wilson - and later recanted - that she felt uncomfortable when the film's co-producer Amanda Ghost asked to have a shower and a bath together.
MacInnes denies making or retracting a complaint, insisting she had not been uncomfortable when the pair shared a bath in their swimwear after Ms Ghost suffered a medical episode in September 2023.
But Wilson has stood by her version of events, claiming in an affidavit that Ms Ghost became angry when the complaint was relayed and called MacInnes a "lying idiot who cannot sing".
The first-time director went further during her evidence in the witness box last week, telling the Federal Court the producer had been so furious there was "spit coming out of her mouth".
At Ms Ghost's prompting, Wilson sought clarification from the young actor, who said she found the situation bizarre but she didn't feel personally uncomfortable.
The Bridesmaids actor reported back to the producer that "Charlotte says all good" and that she had "zero issues", according to texts tendered to the court.
But Wilson states in her affidavit that she had a lingering sense of unease about a situation she deemed "very inappropriate".
"I found Ms Ghost to be obsessed with Ms MacInnes and what had happened," Wilson wrote of the days after she relayed the alleged complaint.
The producer denies asking the young actor to share a bath and shower, revealing in her own affidavit that she was shocked when the accusation was put to her and thought Wilson must have misunderstood.
Ms Ghost maintains she didn't react angrily or describe MacInnes as a liar who couldn't sing.
She also rejected the accusation that she became obsessed with the young star, but agreed she had been confused by what Wilson had told her and it remained on her mind.
Ms Ghost said she came to believe MacInnes' version of events when they met up two weeks after the alleged complaint and the pair reconciled.
MacInnes has been accused of withdrawing the sexual harassment complaint in return for lucrative career opportunities linked to Ms Ghost, including a lead role in a production and a six-figure record deal.
Wilson said she noticed a change in the young actor's demeanour during the check-in phone call the day after the complaint, which she found "very strange".
"I felt like she was guarded and defensive whereas the day before she had seemed upset and forthcoming," she wrote in her affidavit.
"I was worried that someone had said something to her to get her to change her story."
The Hollywood star has denied accusations she fabricated the complaint or raised it for leverage during disputes with her co-producers over the film's budget and writing credit.
Wilson took out defamation insurance after learning she would not be given writing credit so she could "go ballistic on social media", MacInnes' barrister Sue Chrysanthou SC argued.
She told the court Wilson falsely portrayed herself as a whistleblower who spoke up to protect MacInnes when instead she was airing the alleged complaint for her own benefit.
"This is how this bully, apparently this saviour of women, the protector of the harassed, responds," Ms Chrysanthou said.
The trial is set to conclude on Friday with closing statements from both sides.
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