|Police said the girl's story made it clear who was to blame for the attacks in Kano|
The girl, speaking at a news conference organised by police, said she was taken to the city of Kano where two other girls detonated their bombs.
At least four people died in the 10 December attack. The girl was arrested, still wearing explosives, police said.
About 2,000 people have died in attacks blamed on the Islamists this year.
The girl told journalists that her parents had taken her to militants hiding in a forest near the town of Gidan Zana in northern Kano state.
She said one of the leaders asked her if she knew what a suicide bombing was.
"They said, 'Can you do it?' I said 'no'," she said.
"They said, 'You will go to heaven if you do it.' I said 'No I can't.' They said they would shoot me or throw me into a dungeon."
The girl said she finally agreed to take part in the attack but "never had any intention of doing it".
|Scene of attack in Kano market - 10 December|
It was not possible to independently verify the girl's story. Correspondents said she had no lawyer present.
Kano police said they wanted the girl to tell her story to make the public aware of who was behind the attack.
Kano State Police Commissioner Adenrele Shinaba, quoted by Nigerian media, said police wanted to dispel rumours that the attack had been linked to inter-tribal conflict.
Boko Haram, a Sunni Islamist group, has been waging an insurgency in Nigeria since 2009.
In recent months the group has taken control of a series of towns and villages in north-east Nigeria and has vowed to create an Islamic state in those areas.
Nigerian authorities have struggled to defeat them.