Zaneta Krokova, 11, was holding the hand of her 12-year-old cousin Helina Kotlarova when they were hit by a blue Peugeot 807 in Oldham, Greater Manchester.
The girls had just come out of a shop near their homes when they were struck in Ashton Road at around 7.15pm.
Greater Manchester Police said that Miss Krokova died yesterday morning.
Her older cousin was killed at the scene.
The news came after police questioned five men after two girls were mown down in a hit-and-run incident.
Police said five men aged 23, 59, 48, 38 and 18 have been arrested on suspicion of causing death by dangerous driving and are in custody for questioning.
Officers are appealing for anyone who saw a dark coloured Peugeot 807 in the area at the time and the driver of a white van to come forward.
Helina’s mother Sylva and father Robert raced to the scene but she was declared dead by medics as her distraught mother stroked her hair.
On New Year’s Day, the family of seven sisters and one brother, who came to England from the Czech Republic eight years ago, sat in tears mourning Helina.
Her father sat with his head in his hands, his wife weeping, while other red-eyed members of the family sat in silence in the kitchen of their terraced home.
Helina’s sister Sylva, 19, told how the family rushed to the scene 100 yards from their home seconds after the crash.
She said: “Her face was all bloody. She did not breathe. Mum was touching her hair.”
The driver of the car did not stop and a police hunt for him was launched. Miss Kotlarova said the girls were with a larger group of family and friends who had already crossed the road, one of the main routes in and out of Oldham town centre.