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 withdrew a sexual harassment complaint to advance her acting and music career.
Wilson alleges the young actor confided - but later recanted - that she felt uncomfortable when the film's co-producer Amanda Ghost asked to have a shower and a bath together in September 2023.
MacInnes denies making, or walking back a complaint, insisting she never said she felt uncomfortable.
Wilson denies accusations she fabricated the complaint to sow division or raised it for her own purposes, rather than out of concern.
"I received no benefit from this experience that led to a court case," the Bridesmaids star told the Federal Court on Thursday.
"All I have done is told the truth at significant cost to myself, at significant detriment."
During her third consecutive day in the witness box, Wilson claimed she had been bullied and harassed because she continued to tell the truth to people, some of whom are extremely rich and powerful.
When it was suggested she herself is rich and powerful compared to MacInnes, Wilson retorted the young actor appears to be enjoying a luxurious, international lifestyle.
She claimed MacInnes withdrew her complaint against Ms Ghost in exchange for "huge enticements" including a lead role in a stage production and a record deal.
"She's changed her story, she's flip-flopped and she's been given huge benefits," Wilson told the court.
She repeatedly insisted she told the truth in the social media posts that are the subject of what she deemed a "baseless defamation lawsuit".
"I am known as a truth-teller," the actor attested.
Posting the Instagram stories to her 11 million followers was not intended to attack MacInnes, she said, but it doesn't appear to have harmed her.
"I don't classify it as an attack, I classify it as telling the truth," Wilson told the court.
But MacInnes testified she felt bullied and intimidated by the older actor and blamed her for organising a cyber attack on her social media account that led to a nude photo being leaked.
The Deb's lead actor revealed her Snapchat account was breached and there was an attempted breach of her Facebook account days after she filed legal proceedings against Wilson in September 2025.
"I believe this was orchestrated by Rebel," she wrote in an affidavit.
"It was completely terrifying and caused me a new kind of anxiety."
Wilson rejected the accusation when it was put to her by MacInnes' barrister Sue Chrysanthou SC.
"That is an absolutely outrageous statement to make in court that I moonlight as a hacker," she replied.
When pressed on whether she had directed someone else to carry out the breach on her behalf, Wilson responded "obviously not".
She similarly batted away a suggestion that she stalked the young actor to ascertain her whereabouts as absolute nonsense.
Ms Chrysanthou has argued Wilson falsely portrayed herself as a whistleblower who sought to protect MacInnes when she was instead using the alleged complaint as leverage in a commercial dispute with her co-producers.
Wilson has rejected the suggestion, maintaining that she regards herself as a champion of women.
She concluded her testimony on Thursday afternoon.