Maralal, Kenya (CNN) Singing and dancing as she performs in a school assembly, Younis looks for all the world like a typical Kenyan teenager, with a beaming smile and a grey and maroon uniform.

There's little outward clue to the trauma she's already been through in her 13 short years. When she was just nine years old, Younis's parents arranged for her to marry a man old enough to be her grandfather, in accordance with local Samburu tradition.

The Samburu are an ancient Kenyan tribe pastoralist cattle herders, said to be "distant cousins" of the Maasai. Even to outsiders, their languages and customs are strikingly similar.

Younis and other girls like her have dared to break away from some of these traditions -- child marriage, female genital mutilation and beading (the practice of promising girls to their male relatives for sex) --which are illegal in Kenya.

But in doing so they risk being disowned by their families and communities.

"When I was about nine years old, my father married me off to an old man who was 78 years old," Younis explains, the memories of her harrowing experience still raw. "I went to his home and I stayed with him one week.

"He told me that I will be a wife but I was just innocent, I wanted to come to school. But that man wanted me to be a third wife. I told him, I will not be your wife, and he caned me.

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"Then I heard that there is a woman who helps children. I came from Baragoi barefoot, I didn't even have shoes that day. I came to Maralal ... Kulea took me to [the] children's office, she rescued me."

There are eight other girls at Younis's boarding school just like her; all have been brought to safety by Josephine Kulea and her Samburu Girls Foundation

To these girls, and some 200 others across Kenya, Kulea is "Mama Kulea." When their families refuse to have anything more to do with them, she takes the place of their mothers.

Kulea is fighting against the very Samburu cultural traditions she grew up with. She says she began asking questions about what was happening in her community after attending boarding school and studying for a nursing degree in a different part of the country.

"I realized we are the only ones doing FGM, female genital mutilation, the other communities [are] not doing it," she explains. "I ... came to realize that there are things that are not right and I need to make a difference, that's how I started rescuing girls."

And she began, in 2011, by looking very close to home.

"My first rescue was my two cousins," she explains. "One was 10 years old and she was the one getting married; most of the time in my community, when the girl is getting married young, that is when they undergo female circumcision. I was alerted that she was going to get married, so I went and rescued her, and after I rescued her I took her to school.

"Two days later I get a call and am told there was a wedding in that village, and am like, 'I have the girl, so who got married?' They said it's the little sister who was seven years old -- they replaced her because the cows were here and any girl had to go."

Kulea rescued the second girl, and saw to it that her uncles were arrested -- because FGM and early marriage were made illegal in Kenya in 2011, the law is on her side and she works alongside the police, but that doesn't mean that what she does is without risks.

The parents and relatives of girls she rescues are often detained for just a short period of time, and many in the Samburu community do not like the changes she is working to bring about.

"Growing up from this community, everyone looks at me like, 'You should be like us, you should not be fighting us," she explains. "It's a risk for me but I still give it a go."

For now, though, there are still many girls in need of help; in one manyara, or temporary village built by the Samburu in different locations according to the season, a group of mothers has called on Kulea for assistance.

The remote manyara is at the end of a brand new dirt road, built just a month ago. There is no electricity or running water, and the nearest school is too far away for any of the children to walk to; only 5% of the Samburu community can read and write.

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To reach out to people, Kulea hosts a radio program, which is how the mothers in this village heard about her; the girls here are already "beaded," promised to local men in exchange for bead necklaces -- the youngest is just seven.

"All the girls in the village are at risk," she says "This one is nine years old but they want [to] marry her off. That's why they are asking for her to go to school."

Girls are bought for sex by a member of the same clan before they are married off. The more beads she has around her neck, the higher the price. Once girls reach the age of marriage they will marry someone from a different clan. If the girl falls pregnant before that to one of her relatives, she may be forced to undergo an abortion; if she has the child, it is unlikely to be accepted by the community.

And although female genital mutilation and early marriage are illegal in Kenya, cultural traditions are hard to break.

Angela, 12, was rescued by Kulea after seeing her friends undergo FGM; she says she saw blood and heard screams, and did everything she could to avoid meeting the same fate.

"When I was nine years old, my father wanted me to be circumcised," she says. "I ran away to the forest."

Kulea is proud of her Samburu heritage -- decked out in her tribal dress, singing and dancing at a traditional graduation ceremony that much is clear. She simply believes that women and girls like Angela and Younis have a vital role to play in the community, and wants to see them given that chance.

"There is hope. And I know when we take more kids to school in future there will be a difference in my community."