Humiliated and scared of being attacked again, the teenager fled from Kilifi county to live with her sister in nearby Makueni county where she returned to her studies and her dream of being a lawyer. She also began campaigning for girls' rights.
In New York on Friday to witness the United Nations adopt a new set of global goals that includes empowering all women and girls, Jacinta, 17, said two of the biggest problems facing girls her age in Kenya were rape and early marriage.
"When I was attacked my grades started going down and I couldn't concentrate at school. I felt so ashamed ... I used to hate myself," Jacinta told the Thomson Reuters Foundation on a hotel terrace overlooking Manhattan on her first trip outside Kenya.
"I want to see girls' rights respected. We need to fight all forms of discrimination against girls and women."
Jacinta was one of nine girls from Kenya, Pakistan, Brazil and the Philippines flown to New York by child rights group Plan International to be present as 193 UN member nations committed to a roadmap for change over the next 15 years.
The United Nations' 17 Sustainable Development Goals (SDGs) set out an ambitious vision to end poverty and hunger, and protect the planet, but also to achieve equality for women in all walks of life and a better education for girls.
A standalone goal commits countries to achieving gender equality and empowering women and girls, with targets to end child, early and forced marriage, female genital mutilation (FGM), and all forms of violence against women.
Figures from campaign group Girls Not Brides show more than 15 million girls worldwide are married before they turn 18.
Child marriage deprives girls of education and puts them at risk of serious injury through early childbirth.
Worldwide, more than 130 million girls and women have undergone female genital mutilation, which involves the partial or complete removal of the external genitalia and is considered a necessary pre-marriage ritual for girls in some countries.
While the SDGs aim to end child marriage and FGM, supporters acknowledge that measuring progress will be tricky as success would mean tackling deeply entrenched attitudes towards girls and women, and their place in society.
Shelby Quast, director of the Americas office for Equality Now, called for a worldwide indicator on female genital mutilation to track progress.
"Globally, there continues to be a huge gap between what governments commit to do and what happens in practice," she said.
Plan International CEO Anne-Birgitte Albrectsen said the challenges should not be underestimated, but neither should the opportunities offered by the SDGs, which are designed to help shape government policies and projects from now until 2030.
"For the first time ever, we have the potential to end poverty in our lifetime - it is within our grasp. However, this can only be achieved by recognising the potential of girls," Albrectsen said in a statement.
For Jacinta, wide-eyed at the skyscrapers of Manhattan and excited about trying new foods, now is the time for change.
"Girls need to be valued as much as boys and families must invest in our education," she said. "It's high time we let world leaders know we are ready to fight for our rights."