Diarra, 30 at the time, spoke to Diakhate's father and arranged for her to stay in her family home until she was 15. It wasn't long after she eventually joined him in Keur Issa, a hamlet in western Senegal, that she became pregnant.
Forty years later, sitting in the courtyard of the matrimonial home, Diakhate explained how she went on to have 12 children.
"In those days, when parents saw their children getting married they were very happy," said Diakhate, now 55. "Since we girls were not educated, we were also happy to get married. We didn't know early marriage was not a good thing."
Child marriage is widespread across sub-Saharan Africa, where it is often driven by endemic poverty and seen as a way of securing a girl's future both financially and socially.
It also benefits parents through the payment of a "bride price".
A recent study by children's charity Plan UK found that 43 percent of girls in West Africa are married before their 18th birthday. Not only are they pulled out of school, but many face early pregnancy and serious health complications.
Diakhate didn't attend any kind of school until her forties, when she took adult literacy classes as part of a community programme run by local aid agency Tostan.
During the 30-month course, she and other women in the village learned how to read and write in Wolof, Senegal's main language.
They also studied reproductive health and learned about obstetric risks for still-developing girls' bodies, including a common childbirth injury called a fistula that affect about 2 million women and girls, mostly in Africa. A fistula causes severe incontinence.
Experts say female genital mutilation, common in Senegal, exacerbates those risks.
"We realised there are lots of problems with child marriage and that it wasn't good at all for girls to be married early," Diakhate said.
Diakhate went on to become a community leader, rallying the women of her village against child marriage on the grounds that it put girls' lives in danger and denied them an education.
She spoke to the village chief, the local imam and the municipal councillor about the women's wish to see an end to the practice.
But the men were not convinced. They accused her of corruption, saying she had been paid by Tostan to destroy their ancestral traditions.
"I don't get paid -- I'm a volunteer," said Diakhate, her face still clouding at the accusations all these years later. "They sent me death threats saying they would use gri gri (magic) against me."
Despite the hostility, Diakhate pressed on. After several months of talks with community leaders her resilience paid off when in late 1998 the entire community decided to abandon child marriages.
Not a single child marriage has taken place in Keur Issa since.
Several other communities in Senegal have also banned the practice. The latest is a cluster of 159 communities in the Fouta and Kolda regions, which also abandoned female genital mutilation.
"As women and mothers we talk to our daughters ... We advise them to go to school," Diakhate said. "We don't want them to suffer the same fate as us."