Contreras was just one of hundreds of children who disappeared under a variety of circumstances during El Salvador's brutal, 13-year civil war, which left some 75,000 people dead and thousands more missing. In most cases, the parents have yet to find out what happened to their children, while a few hundred of the missing have been identified after giving investigators DNA samples and other evidence.
Now, a human rights group, Probusqueda, is uncovering another macabre and mostly unknown twist to the tragedy. In Contreras' and at least nine other cases, low-to-mid-ranking soldiers abducted children in what an international court says was a "systematic pattern of forced disappearances." Some of the soldiers raised the children as their own, while others gave them away or sold them to lucrative illegal adoption networks. In Contreras' case, an army private spirited her away, raped her and gave her his own surname.
The crimes make El Salvador the second Latin American country proven to engage in such child abductions during internal Cold War-era conflicts. Argentina's military kidnapped hundreds of children of political opponents, and the prosecution of those responsible three decades later led to the indictment of top officers, including army Gen. Jorge Rafael Videla, then-head of Argentina's military junta.
Contreras and eight other victims of military abductions successfully sued their government in the Inter-American Court of Human Rights, demanding the military release more information. Three years later, the military hasn't turned over the requested files and the officers, most of them retired, suspected of adopting stolen children have refused DNA tests.
"Without those files we can't say this or that officer is responsible," said the country's attorney general, Oscar Luna.
President Mauricio Funes has tried to made amends for some civil war-era crimes, said Probusqueda director Maria Ester Alvarenga. The president belongs to the Farabundo Marti National Liberation Front party, which began as the guerrilla force battling El Salvador's U.S.-backed government, and could be expected to pursue such prosecutions.
"But it's surprising to me that he isn't making the military archives available," Alvarenga said. "I'm frustrated that nothing's been done at these levels."
Several Latin American countries have hit stiff opposition from the military when they've tried to prosecute soldiers and officers for human rights abuses. In the cases of Argentina and Chile, prosecutors have succeeded in indicting and jailing top officials.
In El Salvador, Alvarenga said, the military "is a real power."
So far, the initial investigations have hinted at the possible enormity of the abuses.
Over the past 20 years, Probusqueda has received 921 reports of children who went missing during the war, with many killed in combat and others orphaned when their parents died. The human rights group has identified the parents of 382 of the missing through DNA tests, and of those, 235 have reunited with their families. Another 95 are waiting to meet their parents, while 52 have been found dead.
The majority of the cases, 529, remain unsolved.
A government missing-persons commission created in 2010 by order of the Inter-American court has also received 203 reports of missing children, with some of those cases likely duplicating Probusqueda's. Just last year, the commission investigated 124 cases and found 15 of the missing. Two of the children were located in Italy, and another was in the United States. Investigators found the corpses of eight children who had been killed and buried during the war.
According to Contreras and other sources, she, her siblings and nine other children were seized in 1982 as the U.S.-trained anti-guerrilla Atlacatl battalion clashed with rebels. A helicopter took away the boys, while the girls were driven away in trucks.
Army Pvt. Miguel Angel Molina ended up with Contreras and later registered her as his own daughter in the western Salvadoran town of Santa Ana, according to the Inter-American court, which also found that he had raped her.
"[The situation] put her in a state of extreme vulnerability that aggravated her suffering, acts of violence that she suffered during almost 10 years, that is to say, between the ages of 4 until 14 years," the court ruling says. Molina later committed suicide.
The court found the Salvadoran government was responsible for the abductions of not just Contreras but also of her two siblings Serapio Cristian, who was 20 months old at the time of his kidnapping, and Julia Ines Contreras, who was 4 months old. The court also found the government responsible for the abductions of three other children who were between the ages of 3 and 14.
"That soldier stole everything from me," Contreras said. "He took away my parents, he took away my siblings, he took away my identity. I couldn't live like a girl because he never gave me the love of a father and he was always abusing me, even raping me. I was only 10 years old and I couldn't do anything."
Victims and investigators said justice won't be completely served until El Salvador's government carries out the entirety of the court's orders.
That includes taking responsibility for the abductions of Contreras, her siblings and the three other children mentioned in the court ruling, and investigating and trying those believed responsible. El Salvador has also been ordered to locate the four in the group of missing still unaccounted for, provide medical and psychological support to the victims, issue a public apology, name schools after those abducted and open government archives about the history.
In an Oct. 29 ceremony attended by Contreras, then-Foreign Minister Martinez Hugo Martinez fulfilled part of the order. He asked for forgiveness from "hundreds of Salvadoran families who were victims of the forced disappearances of boys and girls" and "who suffered the infinite pain of being hit by the disappearances of their most beloved and vulnerable people."
Yet Contreras' sister has never been found, and despite promises by the country's Foreign Ministry to name schools after victims, it hasn't indicated when it will start doing that.
The armed forces remain the chief obstacle to justice, said Miguel Montenegro, director of the nonprofit Human Rights Commission.
"Here, there's a strong power, a power exercised by old members of the armed forces," Montenegro said.
For Contreras, the quest for truth has been long, bitter and incomplete.
She eventually escaped Molina and stayed with one of his relatives. With the help of another of Molina's relatives, Contreras settled in Guatemala.
Her parents found her in 2006 after they appealed to Guatemalan officials and Probusqueda. Just recently, she reunited with her brother, who was also abducted and given to a soldier's relative. She has also started her own family.
But Contreras remains distant from her parents and has yet to find her sister.
"I recovered my identity," Contreras said. "The other Gregoria doesn't exist. I have my husband and my children. I don't want anything more."