Dembrowski said the couple frequently argued, and she would book an extra room for Depp when he traveled with his wife so he would have somewhere to go and "hide."
Heard frequently insulted to Depp, calling him an "old fat man" and belittling him, for example, when she was told that Dior planned to use him in an advertising campaign, Dembrowski said.
"She said, 'Dior, why would Dior want to do business with you? They're about class and they're about style and you don't have style,'" she said.
Dembrowski also testified that Heard had a tendency to "exaggerate" her brother's issues with drugs and alcohol and she had never seen him go on a "bender."
Chew said the allegations of domestic abuse had hurt Depp's career.
"For nearly 30 years, Mr Depp built a reputation as one of the most talented actors in Hollywood," Chew said. "Today his name is associated with a lie, a false statement uttered by his former wife.
"Hollywood studios don't want to deal with the public backlash from hiring someone accused of abuse," he said. "A false allegation can devastate a career."
Depp filed the defamation complaint against Heard in the United States after losing a separate, high-profile libel case in London in November 2020 that he brought against The Sun for calling him a "wife-beater."
In 2016, Heard sought a restraining order against Depp. Their divorce was finalized in 2017, with Heard receiving a $7 million settlement.
A panel of seven jurors and four alternates is hearing the case between Depp and Heard, who had a starring role in "Aquaman."
Both Depp and Heard are expected to testify, along with actors James Franco and Paul Bettany and billionaire Tesla and SpaceX chief Elon Musk, Heard's former boyfriend.
The trial, presided over by Judge Penney Azcarate, is expected to last several weeks.
