President Trump’s younger daughter, Tiffany Trump, made a rare public appearance at her father’s trial at Lower Manhattan Tuesday, after a key witness, Michael Cohen, last week discussed his role in defusing a plot to “extort her” while Mr. Trump was president. 

Ms. Trump, along with other members of the former president’s family, including his sons Donald Trump Jr. and Eric Trump and his daughter-in-law, Lara Trump, who is now co-chairwoman of the Republican National Committee, appeared solemn-faced at court for closing arguments Tuesday.

The former president’s third and current wife, Melania Trump, his youngest son, Barron, and his elder daughter, Ivanka, have been absent from the trial, which centers on hush-money allegedly paid in 2016 to a porn star, Stormy Daniels, whose real name is Stephanie Clifford, to keep her from publicizing a one-time sexual encounter she claims to have had with Mr. Trump in 2006 at a celebrity golf tournament at Lake Tahoe.

Ms. Trump’s appearance came after Mr. Trump’s former fixer, Cohen, disclosed in testimony last week that she had been the subject of an alleged extortion plot involving photos.

In testimony on Thursday, an attorney for Mr. Trump, Todd Blanche, pressed Cohen during cross-examination about the alleged extortion attempt in order to show that Cohen had many reasons to communicate with Mr. Trump, who was by then the president, beyond reimbursing the alleged hush-money payment.

“You agree with me, right, that you had a lot going on both in your personal life and with President Trump in those first two weeks of October?” Mr. Blanche said.

Cohen answered that he agreed with him.

Mr. Blanche added, “You recall on October 25th, you recall her communicating with you concerns about somebody trying to blackmail her?” He characterized the call as a “potential extortion attempt.” Cohen again agreed.

Mr. Blanche also noted that Mr. Trump was coordinating an opening for a new hotel at Washington, D.C., in late October, suggesting that there were at least three topics Cohen could have been meeting with Mr. Trump to discuss.

“So was fixing Tiffany Trump’s situation important to you?” Mr. Blanche said.

“It was important I take care of things but it was not personally important to me,” Cohen said.

“Wouldn’t that be something you updated her father about when you spoke the next morning?” Mr. Blanche asked, to which Cohen replied, “No sir.”

In October 2016, as Cohen was working to pay Ms. Clifford, Ms. Trump joined her father, her half-sister, and her half-brothers — other than Barron — for a sit down interview with a former aide to President Clinton, George Stephanopoulos, about the opening of the new Trump hotel at Washington. During the interview, a rare public appearance for Ms. Trump, she said she was applying to law school and hoped to join the family business.

In the intervening eight years, Ms. Trump has graduated from law school at the prestigious Georgetown University Law Center at Washington, and married the scion of a wealthy Lebanese family with major business interests at Lagos. She has 1.3 million followers on Instagram, where she most recently posted pictures from her nuptials. It’s unclear what Ms. Trump is doing professionally and whether she’s passed the bar — and, if so, where.

She is the daughter of Mr. Trump and his second wife, Marla Maples. Her father’s messy 1990 divorce from his first wife, Ivana, sparked by his affair with Ms. Maples, became legendary in the annals of tabloid journalism, setting a precedent for coverage of future high-wattage divorces.