It happened at 11:50 p.m. Saturday at a home in the 1100 block of West Rockland Street.
Officers arrived to find Daneeka Snipe, 19, stabbed once in the neck.
Medics rushed her to Albert Einstein Medical Center where she was pronounced dead.
Police say 19-year-old Shaliyah Snipe, a cousin of the victim from the 4600 block of Leiper Street, turned herself to homicide detectives the next day.
She has been charged with murder and possessing an instrument of crime.