Melania Trump in Italy last week. A quiet first lady, she has reserved many of her public statements for defending her family. (Luca Bruno/AP)

It is rare for Melania Trump to issue a statement of any sort. The first lady, who has sometimes seemed reluctant about her new role, prefers privacy and restraint.

Yet she chose to speak up forcefully Wednesday, nearly a full day after a gruesome photo of comedian Kathy Griffin holding a prop made to resemble the bloody, decapitated head of President Trump was posted online.

On Tuesday, the photo was condemned by a bipartisan chorus of politicians and pundits as soon as it went public; hours later, Griffin apologized in a video statement. The Trumps did not seem to accept the apology, with the president tweeting the next morning that his children, “especially my 11 year old son, Barron, are having a hard time with this. Sick!”

But the first lady issued a longer statement midday Wednesday: “As a mother, a wife, and a human being, that photo is very disturbing. When you consider some of the atrocities happening in the world today, a photo opportunity like this is simply wrong and makes you wonder about the mental health of the person who did it.”

While the president often blasts his opponents on Twitter, it is rarer for his wife to join him. She refrained from using social media during the first weeks of his presidency and generally stayed out of the political fray during his campaign.

However, her decision to weigh in is in line with her burgeoning approach to public life. She pushes back hard in defense of her reputation and her family.

In November, she threatened to sue a YouTuber who posted video speculating that her son had autism. The video was removed.

She also filed a lawsuit against a Maryland blogger and British newspaper that published articles falsely alleging she had worked as an escort. The articles were retracted and the lawsuit settled in her favor.

One of Mrs. Trump’s first tweets on her @FLOTUS account was to send a thank-you tweet to fashion model Emily Ratajkowski, who had complained that a New York Times reporter was spreading the escort allegation in private conversations. “Applause to all women around the world who speak up, stand up and support other women! @emrata #PowerOfEveryWoman #PowerOfTheFirstLady,” Mrs. Trump wrote.

It often falls to first ladies to guard their family’s private lives. Michelle Obama’s press secretary sternly warned the Ty company when it produced Beanie Babies in the likeness of her daughters. Laura Bush defended her daughters, who made news when they were caught drinking underage. “They just want to do like every other teenager does,” Bush often said.

Hillary Clinton was said to be upset by a SNL “Wayne’s World” sketch that poked fun at preteen Chelsea Clinton, who wore braces. Mrs. Clinton did not issue a public statement on the segment, but word got back to the show that the first lady did not like it.

Similarly, a friend called Mrs. Trump a “fierce wife and mother” and she has said her priority is protecting her son. A report in TMZ, that was corroborated by the president’s tweet, said that Barron Trump was shaken by the photo of Griffin, which he saw while watching television at home with his mother.

“This is a first lady we rarely hear from on anything … so possibly she was thinking of her son,” said Katherine Jellison, a history professor at Ohio University who has studied first ladies. “All the [modern] first ladies who had younger children were really concerned with protecting the kids from the slings and arrows of life in the White House.”