"Nusrat Jahan Rafi's death highlights the need for the Bangladesh government to take survivors of sexual assault seriously and ensure that they can safely seek a legal remedy and be protected from retaliation."
Police handling of the case has compounded public anger. A video of Rafi, from Feni, 160km south of Dhaka, filing her complaint reportedly shows a police officer telling her the incident was "not a big deal".
According to the BBC, she appears distressed in the video and tries to cover her face with her hands.
The police video was then leaked to local media, leading to death threats against Rafi.
Pressure on her to withdraw the complaint worsened after the headmaster was arrested.
On April 6, as she tried to enter her school to sit her final exams, she was lured to the roof and surrounded by four people in burqas, demanding she renounce her accusations.
She refused and they set her on fire, attempting to make it look like suicide. But she was still alive when she was found, only dying four days later.
The brutal case has shocked Bangladesh to its core.
Sheikh Hasina, the Prime Minister, expressed deep personal sorrow and ordered law enforcement agencies to find the perpetrators and bring them to justice.
To date, 15 people have reportedly been arrested, seven allegedly involved in the murder, and one has confessed. The headmaster remains in custody and the police officer who filmed Rafi has been removed from his post and transferred to another department.
However, human rights groups say the case highlights a wider problem of the ongoing vulnerability of women who suffer sexual harassment in deeply conservative Bangladesh, and are targeted when they brave social stigmas to speak out.
"Nusrat Jahan Rafi's cruel death is a sobering reminder of the pervasive risk of sexual violence that is faced by Bangladeshi women and girls," said Ganguly.
"The government should ensure justice for her family, urgently put legal protections in place to prevent sexual assault, and provide effective protections to survivors."