Amalija Knavs, a former Slovenian factory worker who became a United States citizen with help from one of her daughters, Melania Trump, has died. She was 78.

Her death was announced on Tuesday night by Mrs. Trump, the former first lady, on X. No cause was given.

During a New Year’s Eve party at his residence and private club, Mar-a-Lago, in Palm Beach, Fla., Mrs. Knavs’s son-in-law, former President Donald J. Trump, said that Mrs. Knavs was “very ill” and that Mrs. Trump was with her mother in a hospital in Miami.

Mrs. Knavs and her husband, Viktor, became naturalized U.S. citizens in August 2018 under a process in which adult citizens can help their relatives obtain green cards and gain permanent resident status. Mrs. Trump had been their sponsor.

But months earlier, Mr. Trump had denounced that process as “chain migration” and wrote on Twitter, now X: “CHAIN MIGRATION must end now! Some people come in, and they bring their whole family with them, who can be truly evil. NOT ACCEPTABLE!”

Michael Wildes, an immigration lawyer for the Knavses, said at the time that the Knavses had met the five-year requirement to have green cards before seeking citizenship.