The Pitch Perfect star is being sued by Charlotte MacInnes, the 27-year-old lead actor of the musical comedy The Deb.
MacInnes claims she was defamed by Wilson in social media posts that suggested she is a liar who retracted a sexual harassment complaint to further her acting and music career.
Wilson claims the young actor confided that 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 was pretty shocked by it," Wilson told the Federal Court during the first day of her evidence on Tuesday.
"I took it as a sexual harassment complaint."
Work had been underway on The Deb for years and shooting was just weeks away at the time, the actor told the court.
"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 said.
The conversation allegedly occurred a day after MacInnes shared a bath with Ms Ghost in their swimwear in a bid to warm up after the producer suffered a medical episode at Bondi Beach.
MacInnes denies making a complaint to Wilson and insists she never said she felt uncomfortable.
The Bridesmaid star says she asked the young actor if she was alright and reported the matter to another producer before escalating it higher at a later date.
She will continue to give evidence on Wednesday, when she is expected to be grilled about the aftermath of the alleged complaint.
In her affidavit, the first-time director wrote that she overheard the producer and young star saying things of a sexual nature to each other, which MacInnes has rejected as untrue.
It is likely Wilson will face questioning about a claim MacInnes made in her own sworn statement that the older actor had directed a cyber attack on her social media accounts.
MacInnes alleges her Snapchat account was breached and there was an attempted breach of her Facebook account just days after she filed legal proceedings against Wilson in September last year.
The hack led to a nude photo of her being leaked to all of her contacts, she claims.
"I believe that this was orchestrated by Rebel," she wrote in her affidavit.
There has not yet been evidence aired in open court to support her claim and Wilson has not been quizzed about it.
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