Elizabeth Warren, who cracked open a beer on-camera and took some questions from her followers on New Year's Eve in a spontaneous livestream posted on Instagram that channeled similar social-media efforts of the young and hip.
Trump revived one of his favorite nicknames for Warren and even jabbed at her husband, saying he should have been "dressed in full Indian garb".
Mr Trump has long derided Ms Warren, a Democratic senator, as "Pocahontas" over her claims about her heritage.
In a tweet shared by nearly 20,000 people, Mr Trump said the 2020 presidential hopeful, who claims to be part Native American, should shoot a political advertisement from "Bighorn or Wounded Knee". Elizabeth Warren (D-Mass.) made after announcing her candidacy for president.
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The Wounded Knee massacre occurred in South Dakota, in 1890, where at least 150 and possibly up to 300 Lakota were killed after US soldiers opened fire at an encampment while trying to disarm the tribespeople.
Native American leaders have called Mr Trump's past attacks on Ms Warren offensive and distasteful. To Native Americans, Trump is an immigrant.
That wasn't Trump's only late-night tweet on Sunday that drew notice for its racial overtones.
The test results revealed Warren likely has trace amounts of Native-American ancestry. Shortly after his Wounded Knee messages, Trump posted two tweets quoting from a Pat Buchanan column to support his push for a wall on the southern border.
"A DNA test is useless to determine tribal citizenship", Secretary of State for the Cherokee Nation Chuck Hoskin Jr. said in a statement after Warren released the test. "On behalf of the Rosebud Sioux Tribe, I condemn President Trump's racist and disrespectful tweet about this brutal incident, in which an estimated 300 unarmed men, women, and children were rounded up and slaughtered".