Katharina Harf, co-founder of the bone marrow donor center DKMS, says Shannon Tavarez died Monday at Cohen Children's Medical Center in New Hyde Park, on New York's Long Island.
Tavarez had received an umbilical-cord blood transplant in August.
Stars including Alicia Keys, Rihanna and 50 Cent had campaigned to help Tavarez find a bone marrow donor. Cast members held donor registration drives. A perfect match wasn't found.
Tavarez was forced to quit the show in April.
She beat out hundreds of other hopefuls last year to earn the role.