Erica had suffered major brain damage from a massive heart attack on Christmas Eve.
Her mother, Esaw Snipes-Garner, said her daughter went into cardiac arrest during an asthma attack and had since been in a coma.
Snipes-Garner says her daughter suffered her first heart attack not long after giving birth to a baby boy in August. Doctors said the pregnancy had put a strain on her heart, which was later found to be enlarged.
Eric Garner died after a police officer subdued him with a chokehold in 2014. His last words were "I can't breathe," which became a slogan for activists.
Erica appeared in campaign commercials for Senator Bernie Sanders during his 2016 presidential run.
The Rev. Al Sharpton, in announcing Garner's death Saturday, says she fought for justice and was "a warrior to the end."
Sharpton discussed the death of Erica Garner:
Garner's official Twitter account, run by her family and friends since she became ill, asked that she be remembered as a mother, daughter, sister and aunt with a heart "bigger than the world."
(Some information from the Associated Press.)