A lawsuit filed by Melania Trump depicts her heightened profile as a “unique, once-in-a-lifetime opportunity” to make millions of dollars in business, once again raising questions about the relationship between President Trump’s official role and his family’s business interests.

Mrs. Trump’s suit, filed on Monday in a New York State court, accuses The Daily Mail, a British tabloid, of libel for reporting last year on claims that a modeling agency she worked for in the 1990s was also an escort service.

The new complaint does not refer explicitly to the White House or Mr. Trump, or even her status as a candidate’s wife when the article was published and now as first lady. Instead, it refers to opportunities she had “to launch a broad-based commercial brand in multiple product categories, each of which could have garnered multi-million dollar business relationships for a multi-year term during which plaintiff is one of the most photographed women in the world.”

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Because of the Daily Mail article, it says, “plaintiff’s brand has lost significant value,” greatly reducing those opportunities. It claims $150 million in damages.

A spokeswoman for Mrs. Trump said she was not trying to make money from her role as first lady.

Mr. Trump has fended off criticism that his business dealings around the world create conflicts of interest in his official role, and he has put his adult sons in charge of his businesses rather than sell his assets or put them into a blind trust. On the day he took office, the White House altered its online biography of Mrs. Trump, after complaints that the original wording promoted her line of jewelry.

The Daily Mail published its article on Mrs. Trump on Aug. 20, quoting from a report in a magazine in Slovenia, Mrs. Trump’s native country, and a book about her. She and her representatives have insisted that the claims it repeated are false.

On Sept. 1, Mrs. Trump sued The Daily Mail in a state court in Montgomery County, Md., and on the same day, the tabloid published a retraction. Last week, the Maryland court dismissed the case, saying it did not have jurisdiction. The new case against Mail Media, a corporation that operates the Daily Mail’s website, was filed in State Supreme Court in Manhattan, where the company has offices.

Mrs. Trump also sued a Maryland blogger, Webster Tarpley, who published claims like those cited by The Daily Mail. She settled that case on Tuesday, and her lawyer, Charles J. Harder, said in a statement that Mr. Tarpley had agreed to pay Mrs. Trump “a substantial sum as a settlement.”