In the three-minute video, a woman who claims to be Maida Yakubu, one of the 276 schoolgirls kidnapped by Boko Haram in April 2014, is seen wearing a black veil and holding a gun.
Flanked by three other women clad in black, she proclaims her loyalty to Boko Haram, which has been fighting the government since 2009 in an insurgency that has killed over 20,000 people.
When asked by a man in the background why she does not want to return home to her parents, she replies: "The reason is that they live in the town of unbelief. We want them to accept Islam."
But the woman's mother believes she did so under duress.
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"For me, this video is torture," Esther Muntari told AFP today from Chibok. "I haven't slept since I watched it".
"The tie that binds us is unbreakable. It's just not possible that my daughter prefers her kidnappers to me," said the mother of five. Maida is the oldest at 19.
Muntari said the woman mentioned Islam, she "immediately understood that she had been forced to say what she said in the video".
Last week, 82 schoolgirls who were kidnapped three years ago were released in exchange for imprisoned Boko Haram members after negotiations between the extremist group and the government.
Analysts said it was likely that others may have developed sympathies for their captors over time.
"The video has instilled fear in our minds and has somewhat dampened our hope that our girls will be freed," Enoch Mark, whose two children are missing, told AFP.
"I don't think any of our girls would choose to stay with Boko Haram if they were given a choice," Mark said. "The only explanation" is that Maida was "forced to stay".
Testimony from former hostages in the brutal conflict has revealed that Boko Haram forced many women and young girls into marriage, and that rape and sexual violence were commonplace.
"From what we know of other young women who've returned, the relationship with their captors is very complex and at times quite ambiguous," Elizabeth Pearson, a Boko Haram specialist who studies women and conflict, told AFP in an email exchange last week.
Genuine relationships will emerge, as not all fighters behave brutally to the women in the camps, particularly if children are involved, she added.
"It's a much more complex situation than the abducted- rescued-victim narrative we've seen at times," she said.
Fifty-seven escaped in the immediate aftermath. Of the 219 who did not manage to flee, 106 have either been released or found, leaving 113 still missing.
Boko Haram also released a second video on Friday claiming to show five commanders that the Nigerian government freed in exchange for the 82 Chibok girls.
In the video, a man who identifies himself as Abu Dardaa, or Money, says Boko Haram has returned to Sambisa Forest, which was long its stronghold in Borno State, and is preparing to bomb Nigeria's capital city of Abuja.
The Nigerian military said in December that it had driven Boko Haram from Sambisa Forest.
Today, a statement by Brigadier General Sani Kukasheka Usman, an army spokesman, confirmed that the man was among those freed in the exchange, while calling the video "mere propaganda".
"He was a direct beneficiary of the process that led to the release of 82 of the abducted girls, and does not have a say or capacity to do anything, therefore his threats should be ignored," the army said.