Army spokesman Colonel Sani Kukasheka Usman said soldiers freed the girl after a battle in north-eastern Sambisa Forest in which they liberated 97 women and children and killed 35 extremists.
He said she is 157 on a list of 218 girls seized more than two years ago from a boarding school, but Chibok community leader Pogu Bitrus said number 157 has a different name.
The list has two other young women sharing the surname given by the military, and the rescued girl may have been visiting older sisters at the school on the night of the kidnapping, said Mr Bitrus.
The first Chibok teenager to be found was discovered with a four-month-old baby by hunters on the fringes of the Sambisa Forest on Tuesday.
On Thursday, Amina Ali Nkeki, 19, was flown to Abuja to meet President Muhammadu Buhari.
