The sister of the young Michigan woman whose killing has become the latest flashpoint for Republicans on illegal immigration is pushing back on former President Donald J. Trump, criticizing him for using her sister’s death to score political points and contradicting his claims that he contacted the family.

At an event in Grand Rapids, Mich., on Tuesday, Mr. Trump described Ruby Garcia, 25, and her killing at length. The man charged with her death was in the United States unlawfully, according to immigration officials, something that Mr. Trump seized on in his remarks to describe Ms. Garcia as a “beautiful young woman who was savagely murdered by an illegal alien criminal.” He also told the crowd that he had spoken to her family.

But that wasn’t true, the sister, Mavi Garcia, said, adding that the family was upset by what they heard while watching the remarks in real time.

“He did not speak with any of us, so it was kind of shocking seeing that he had said that he had spoke with us, and misinforming people on live TV,” Mavi Garcia, who has acted as a spokeswoman for her family, said in an interview with WOOD-TV8, the NBC affiliate for West Michigan.

She faulted Mr. Trump for framing her sister’s death as a border issue.

“It’s always been about illegal immigrants,” she told the news station. “Nobody really speaks about when Americans do heinous crimes, and it’s kind of shocking why he would just bring up illegals. What about Americans who do heinous crimes like this?”

Mr. Trump, at the rally in Grand Rapids, brought up Ruby Garcia and other victims of violent crimes as he railed against what he called a “border blood bath.” He has focused heavily on immigration and the border to try to win over voters by claiming that the influx of migrants at the southern border is contributing to an increase in crime in the United States, a connection that available data does not support.

Mr. Trump described Ms. Garcia in his remarks, saying: “They said she just had just this most contagious laughter, and when she walked into a room, she lit up that room. And I’ve heard that from so many people — I spoke to some of her family.”

He did not make clear whom he had spoken with, and his campaign did not respond to questions about whether he had communicated with any members of the Garcia family.

Mavi Garcia did not return requests for comment from The New York Times, but she told The Washington Post and ABC News that Mr. Trump did not speak with her “immediate family.”

Ruby Garcia, who was found dead on the side of a Grand Rapids highway on March 22, according to local news reports, was one of several victims of high-profile crimes purportedly committed by illegal immigrants that Republicans have sought to highlight.

The police have said that she was dating the man charged with her death, Brandon Ortiz-Vite, 25, who first entered the country unlawfully as a child, according to a statement from U.S. Immigration and Customs Enforcement.

After Mr. Ortiz-Vite was arrested on charges unrelated to immigration in August 2020, he was found inadmissible and deported to Mexico in September 2020, during Mr. Trump’s administration, an I.C.E. spokesman said. The agency said Mr. Ortiz-Vite came back to the United States “at an unknown date and location.”

Court records show that Mr. Ortiz-Vite was charged with homicide and other crimes in the case involving Ms. Garcia, and will appear in court on April 9.

At a campaign event in Georgia last month, Mr. Trump met with the family of Laken Riley, a 22-year-old nursing student at Augusta University, in Georgia, whose body was found in February in a wooded area on the campus of the University of Georgia in Athens. The man charged with her murder is an undocumented immigrant from Venezuela, and Republicans have used Ms. Riley’s death to rally around calls for additional border security measures.

Mr. Trump recently derailed a bipartisan border deal in the Senate by urging Republicans not to support it, in a move that prevented a political win for President Biden and allowed Mr. Trump to continue campaigning on the issue.

On Monday, before the event in Michigan, Mr. Trump referred to Ruby Garcia in a conversation with Justin Barclay, a Detroit radio host, saying: “I’d love to have her family there, if they’d like to be there. It’d be my honor.”

Ahead of his remarks on Tuesday, his campaign distributed packets featuring photos of Ms. Garcia and others they said had been affected by crimes involving undocumented immigrants. During the event, Mr. Trump described Ms. Garcia as an “incredible young woman,” though at one point mistakenly said she was 17 years old.

Local Democrats pre-emptively criticized Mr. Trump for planning to make Ms. Garcia part of his campaign rally.

Senator Debbie Stabenow, Democrat of Michigan, said in a press call on Tuesday morning that Mr. Trump was “exploiting” Ms. Garcia’s death, calling his use of her story to press a political point “shameful.” Some Democrats and local officials have attributed her death to domestic violence.

Speaking with the local station, Mavi Garcia described her sister as a “very happy person, a very generous person” who “could light up a room,” and said that she was disappointed by Mr. Trump’s focus on undocumented immigrants in talking about her sister’s death. The “focus should be on my sister right now, on who she was in life,” Mavi Garcia said.

“After I heard a couple of misinformations that he had said, I kind of just stopped watching it,” she said of Mr. Trump’s remarks.