Tanya Singleton was charged with conspiracy to commit accessory after the fact in the 2013 killing of Odin (OH'-dihn) Lloyd, who was dating the sister of Hernandez's fiancee. Prosecutors accused her of helping a Hernandez co-defendant flee to Florida.
Massachusetts prosecutors said in a court filing Thursday her cancer has progressed despite aggressive therapies.
Singleton's lawyer says he persuaded prosecutors to dismiss the case because of her health.
Singleton is from Bristol, Connecticut. She's halfway through a two-year probation sentence after she pleaded guilty to refusing to testify before a grand jury despite being granted immunity. The judge spared her prison time last year because of her health.
Hernandez denied killing Lloyd but was convicted in April.