The girl, in her teens, was identified as Gourangi Murmu and arrested after her surrender at Manada police outpost under Bisoi police station jurisdiction, about 70 km from here.
She confessed to have chopped off head of a 60-year-old woman whom she suspected of practising withcraft, police said.
Gourangi was suspecting that Ratni Marangi was responsible for death of her brother and illness of another, police said. "Gurangi during her recent examination was also feeling unwell. She held the woman whom she killed as responsible for their miseries," a police man said quoting her statement after surrender.
She used a sharp edged axe to kill the woman, they said.
The victim was identified as Ratni Marangi, a cook at the village anganwadi centre. Marangi was also the mother-in-law of the accused girl`s elder sister.