Charlotte MacInnes is suing the Pitch Perfect actor over social media posts claiming she had complained about feeling uncomfortable after bathing with the producer Amanda Ghost.
The young actor alleges Wilson's posts - which could be seen by her 11 million followers for 24 hours - suggested MacInnes had withdrawn the complaint in exchange for prime acting and music opportunities.
She denies making the complaint and says her reputation has been seriously damaged before she could enjoy the benefits of starring in her first feature film, a musical set in rural NSW and directed by Wilson.
MacInnes had been thrilled to be cast in The Deb during a meeting with Ms Ghost in 2023, marking it as the moment when all of her dreams looked like they would come true.
"Someone believed in me," she told the Federal Court on Wednesday with a smile.
But two years later, the actor had filed defamation proceedings against Wilson over a series of allegedly defamatory social media posts.
MacInnes is expected to discuss the breakdown of her relationship with the Bridesmaids star when she continues giving evidence on Thursday.
She felt isolated after she was asked to leave an apartment where she stayed with Ms Ghost following the airing of Wilson's allegations, her boyfriend Carlo Boumouglbay wrote in an affidavit.
"She also started to be suspicious and thought Rebel might be spreading misinformation about her and spinning some type of story," he said.
MacInnes was upset Wilson made a false claim about her after she felt the older actor had repeatedly been dismissive and disrespectful to her on set, according to Mr Boumouglbay.
Wilson's subsequent social media posts left his girlfriend in tears and "deeply disturbed", he said.
"She thought Rebel was monitoring her at all times," he wrote in his sworn statement.
"She was fearful for her safety and felt vulnerable."
Wilson's conduct "deeply wounded" MacInnes and had left her constantly on edge, her boyfriend said.
MacInnes told the court she has received numerous abusive social media messages over the years, which left her feeling "pretty awful".
"To be completely honest I have received quite a few of these messages over the past few years so I am somewhat numb," she said.
MacInnes claims her professional reputation has been ruined by suggestions she is untrustworthy and prioritised her own career over those of the 300 cast and crew who worked on The Deb.
Wilson denies the posts are defamatory and maintains the young actor made the complaint before retracting it to ensure her future as a performer by appeasing Ms Ghost.
Her barrister Dauid Sibtain SC has argued MacInnes hadn't suffered any harm to her career since the first social media post in September 2024.
MacInnes signed a record deal with Atlantic Records in late 2025, her manager Shoshanna Stone told the Federal Court on Wednesday.
The deal provided for two EPs and included an advance worth $US110,000 ($A154,000), she said.
Ms Stone's high-profile clients include Britney Spears, Shakira, Boy George and Alicia Keys.
She told the court she signed MacInnes to her roster after being informed of the young actor's talent by her friend Ms Ghost.
The up-and-coming performer's second single is due to be released on Thursday.
Her manager rejected suggestions it had been timed to coincide with the court battle.
The Deb was released in Australia earlier in April after legal issues prevented its widespread release following its 2024 film festival premiere.
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