Lubna Hanash was killed in a shooting outside a college near Al-Arrub refugee camp, eight kilometres (five miles) north of Hebron, medics said.
Witnesses said a civilian car with Israeli plates stopped on the main Hebron-Bethlehem road in the southern West Bank and two men wearing military fatigues got out and began shooting towards a nearby Palestinian college. Medics said another two people were injured by gunshot wounds.
A military spokeswoman said troops on a routine patrol had been "confronted by Palestinians with Molotov cocktails" and opened fire in self-defence, wounding several of them.
Meanwhile, a 15-year-old Palestinian who was hit in the face by Israeli gunfire last Friday died of his injuries, an Israeli hospital spokeswoman told AFP.
Saleh Amarin had been seriously hurt by a bullet fired by Israeli troops during clashes in Aida refugee camp, north of Bethlehem.
The two deaths raised to six the number of Palestinians killed by Israeli gunfire since 10 January.