Divya and her sister Mamta, residents a Pakistani refugee camp in Jahangirpuri for the last five years, were returning from a tuition centre with their friend Kavita when the incident happened, they said.
While they were crossing the Shah Alam Bandh Road, the truck hit the trio, killing Divya on the spot and injuring the other two.
Locals caught hold of the driver and handed him over to the police. Divya was declared "brought dead" by the doctors, while the other two girls, who sustained injuries in their legs, were undergoing treatment.
The driver, Manikant, a resident of Bihar, has been arrested, the police said, adding the driver claimed the girls were running while crossing the road and even though he tried to apply brakes, he could not do in time.
Divya and Mamta were students of a government school here and their father worked as a labourer.