Next month will mark the third anniversary of the abduction of more than 270 girls.
The militants are still holding about 195 of the young women.
The pupil, speaking under a pseudonym, told an education conference in Dubai:
"These girls are human beings, not something that we can forget about."The abduction of the schoolgirls in north-eastern Nigeria in April 2014 by the Islamist militant group caused a global outcry - and prompted campaigns about girls' right to education.
But almost three years later most of the abducted Chibok schoolgirls are still being held by kidnappers.
One of the girls who had been seized, using the pseudonym "Sa'a" to protect her identity, said the "world has to do something" to rescue her school friends.
"How would you feel if your daughter or wife was missing? Not one day or two, but three years. It's very painful," she told the Global Education and Skills Forum.
She said that some of the parents of the abducted girls had died and the others were traumatised by their long wait.
Last autumn, 21 of the young women were returned. But Sa'a told the conference of her disappointment that the majority still remained in captivity.
"I remember those girls, but their dreams are now no more,"
she said, recalling their plans for their careers and future lives.Sa'a described the night in April 2014 when Boko Haram militants arrived at her school, burned books and classrooms and forced the pupils into trucks and cars at gunpoint.
Sa'a and a friend had jumped out the back of the truck as it went into a forest.
The girls had hidden overnight and with the help of a shepherd had made their way back to safety.
"I thought I was going to die that night," said Sa'a.
But she said that if she hadn't taken that split-second decision to jump, she would still have been held in captivity and missing from her family.
Sa'a spoke alongside another young woman, using the name "Rachel", whose father and brothers had been killed by Boko Haram in north-east Nigeria.
Sa'a and Rachel called for greater efforts to get the Chibok girls back and to make schools safe from attack.
They said that their experiences had made them more determined than ever to make the most of an education that had been denied to the abducted classmates.