Ada Kelly Alfaro says the cries from friends asking for help still haunt her daughter, Cynthia Phaola Morales, seven years after she survived a fire at a children’s shelter in Guatemala that killed 41 girls.

Cynthia was one of only 15 survivors of the blaze at the Virgen de la Asunción (HSVA), in San José Pinula, just outside Guatemala City, which broke out on the morning of 8 March 2017.

She and 55 other girls had been locked in a tiny room with no food or access to a toilet, as punishment for an attempted escape from the shelter. The fire started when one of the girls set a mattress alight in protest at their treatment. Despite the girls’ pleas for help the doors of the room remained locked for nine minutes.

Rita, a film inspired by the tragic events at the shelter and the failure of the authorities in Guatemala to protect the girls, who were mainly from low-income families, will premiere next week at the Fantasia international film festival in Montreal.

Rita tells the story of a 13-year-old girl who is taken to a state-run home after running away from her abusive father. The centre’s oppressive conditions soon lead Rita and other youngsters to plan their escape to expose abuse.

The act of rebellion by the girls at HSVA is at the heart of the film, says its award-winning writer and director, Jayro Bustamante. “The moment they took matters into their own hands and decided to stand up against these dark beings who take advantage of their fragility, they became heroines.”

Bustamante says what most interested him was the hostility directed towards the girls in the aftermath of the fire. “Our first reaction as a society was to criminalise the girls, to say that they deserved what had happened to them because they were delinquents.”

The film uses fantasy and magic realism to challenge that narrative and create empathy for the girls. “The objective of the film is not only to talk about this case, because that would minimise what really happens with children [in Guatemala], and especially girls. The objective is to talk about our responsibility as a society towards children.”

In January, the trial of eight government officials and police officers charged in connection with the fire finally got under way. They are charged with the abuse of minors, breach of duty and manslaughter.

Edgar Pérez, a lawyer at Bufete Jurídico de Derechos Humanos en Guatemala (the Guatemalan Human Rights Law Firm), which represents 14 of the girls’ families, says the charges do not correspond to the severity of what happened in 2017.

But, he says, the case is significant because it will expose the failings of the country’s child protection system and the attitudes of the authorities towards poorer families and single mothers. “This case reveals who we are as a society,” says Pérez.

The beginning of the trial “offered a ray of hope that we might finally get justice”, says Alfaro. “Justice seemed very far away.”

Cynthia was sent to HSVA in 2016 when she was 13. Her mother was accused of neglect when Cynthia failed to come home from a party at a friend’s house. Alfaro was told by the courts that she couldn’t adequately supervise her daughter because she was a widow and had to go to work.

Alfaro, who had no legal representation, was told Cynthia would receive education, psychological support and medical attention at the shelter, and “that she would be better off than at home”, she says.

Alfaro, who had to wait two months for permission to visit her daughter, soon discovered the promised support was not forthcoming. Cynthia said the food was bad and there was no privacy when using the bathroom. During their periods, the girls had to cut the sponge from their mattresses to use as sanitary towels. Abuses at the shelter, including severe overcrowding, the use of confinement as punishment and physical and sexual abuse, had been documented in multiple reports dating back to 2012.

The trial is expected to last for months, as only one hearing is held each week. Pérez says that from the testimonies given at the trial so far, “if the staff at the home had acted more promptly, many lives would have been saved”.

“In fact, [the fire] could have been avoided altogether if there had been trained personnel, people with conscience [working there] and real policies for the care of children and adolescents in the country.”

Alfaro is determined to see justice for Cynthia, who is now 21 and married with two children, and other survivors, as well as the families of the girls who died. She wants to make sure this never happens again. “My daughter didn’t deserve to be there, she didn’t deserve what happened to her.”

• Rita premieres at the Fantasia international film festival in Montreal, which runs from 18 July to 4 August.