The heart attack she suffered was the result of a massive asthma attack, according to her family.
The Rev. Al Sharptontold NBC New York that Garner died of natural causes Saturday morning at Woodhull Hospital while surrounded by her family.
Eric Garner became a symbol for victims of police brutality in 2014, inspiring the widespread "I Can't Breathe" slogan, which was spurred by Garner's final words as NYPD officer Daniel Pantaleo choked him, a move prohibited by NYPD guidelines.
Garner often marched in anti-police brutality and Black Lives Matter demonstrations, and set up a foundation in honor of her father. Garner, 27, had suffered significant brain damage this week after a heart attack, representatives said. Doctors at the time said the pregnancy put a strain on her heart and that her heart was enlarged.
"Even with my own heartbreak, when I demand justice, it's never just for Eric Garner", she wrote in a Washington Post op-ed previous year endorsing then-Democratic presidential candidate Bernie Sanders.
"She passed away this morning". Eric Garner had argued with officers upon being approached for suspicion of selling loose cigarettes.
Showing up to rallies with allies and giving interviews for major outlets, she used her voice and platform to demand more transparent and accountable policing, speaking out against a lack of it in her father's case.
"They stayed with her to the end - she was a warrior to the end", Sharpton, the president of the National Action Network and an MSNBC contributor, told reporters. A report Thursday said Garner was brain dead with no chance of recovery.
A grand jury declined to indict the officer; the city agreed to pay a $US6 million ($7.6 million) civil settlement. "What do you want from marching?' He was my father", Garner said.
Garner is survived by two children, including her three-month-old son Eric, named after her father.