The Nigeria army announced the rescue of Maiyanga, who has a 10-month old baby, on Saturday.
In a statement by Sesugh Akume, its spokesperson, the advocacy group identified Maiyanga as No 198 on its list of the missing girls.
It said the girl was a school prefect from Askira Uba, and that her twin was still in captivity.
“We welcome news of the return of another of our abducted #ChibokGirls. Reports from the Acting Director of the Army Public Relations, Colonel Sani Usman Kukasheka, state that Maryam Ali Maiyanga was found amongst a group of fellow escapees by troops of 121 Battalion, Nigerian Army, deployed at Pulka, Gwoza Local Government Area, Borno State,” the statement read.
“Preliminary investigations on our part, show that Maryam Ali (Number 198 on our list), a school prefect, is from Askira Uba and was abducted along with her twin, Halima Ali (Number 197), who is yet to return. We shall update the public with more details as necessary.
“We applaud the federal government under President Muhammadu Buhari, the military and other security formations working day and night to rout the terrorists and rescue all Nigerians in captivity.
“The news of the death of the Commanding Officer of the 272 Task Force Tank Battalion, Lieutenant Colonel Muhammed Abu Ali, a highly-rated, young officer and four other members of his team, in a separate incident at Mallam Fatori, is unfortunate and saddening. We send our heartfelt condolences especially to their families, and the Nigerian military.”