This attack comes after the latest claims by the Nigerian government that Boko Haram has been reduced in capability.
The U.N. has repeatedly called for an end to such blatant violations of international humanitarian law.
Boko Haram and its offshoot, Islamic State West Africa Province (ISWAP), have killed thousands and displaced millions in Nigeria.
The Nigerian Christian girl was abducted at the age of fourteen.
The government released a statement that admits Boko Haram and ISWAP targeting Christian communities.
The child warns in the video: 'We won't stop until we take revenge for all the blood that was spilled.'