Rebel Wilson decided to sue the publisher of Woman's Day after a journalist launched an alleged "shakedown" against her over a tweet.
The Australian actor is suing Bauer Media for defamation, claiming a series of articles painted her as a serial liar and cost her movie roles.
Wilson says the "orchestrated, malicious take-down" stole two years of her limited time in the Hollywood limelight and caused her "star meter" to drop.
On the fifth day of the trial, the Pitch Perfect star revealed it was actually a lawsuit against her that convinced her to sue Bauer Media.
Australian journalist Elizabeth Wilson, who has worked for House & Garden magazine, has taken legal action against the actress over a social media post.
But Wilson, the actress, had accused the wrong journalist.
She says it was a simple mistake because there were two Elizabeth Wilsons who had worked for ACP Magazines, now known as Bauer Media.
Wilson says she sent a letter to apologise but received a lawsuit in reply.
"It was a completely innocent mistake," she told the Victorian Supreme Court on Friday.
"I'm extremely sorry. I feel horrible for what I have done.
"I asked if she would meet me face-to-face to apologise.
"But she doesn't want a personal apology. She wants $250,000.
"I can only now describe that as a shakedown."
Wilson said that in Hollywood a "shakedown" is when someone seeks money from someone they think is "super rich".
She said the journalist's lawsuit against her prompted her to sue the Woman's Day publisher, who had caused her and her family deep distress.
The Woman's Day articles claimed the comedy actress had told "pork pies" about her age, which was 34 at the time rather than 29 as some believed.
But Wilson told the jury she had never lied about her age.
"Being an authentic person, I'm proud of how old I am," she said.
"It's just it was in my best interest, being a Hollywood actress, to not publicly disclose my age."
Earlier in the trial, Wilson said the Woman's Day articles, which were later picked up by American magazines, cost her movie roles.
Wilson said DreamWorks sacked her from Kung Fu Panda 3 because she'd become "too divisive" for a family movie.
She had desperately wanted the role of the ribbon-dancing panda Mei Mei, which was later re-recorded by actress Kate Hudson.
The trial is expected to go for another two weeks and will hear from Wilson's mother and siblings, her Australian and US agents, an old school friend and fellow Australian actor Hugh Sheridan.