WORLD athletics body, the IAAF, asked South Africa to carry out gender tests on the 18 year-old after her muscular physique and extraordinary performances sparked speculation that she could be male.
But her mother Dorcus Semenya, a part-time carer, said: "I am not even worried about that because I know who and what my child is. Mokgadi Caster is a girl and no one can change that."
Speaking from her home in the rural village of Seshego, near Polokwane in South Africa's Limpopo province, the mother-of-six told South Africa's Star newspaper: "If you go at my home village and ask any of my neighbours, they would tell you that Mokgadi is a girl.
"They know because they helped raise her. People can say whatever they like but the truth will remain, which is that my child is a girl. I am not concerned about such things."
Semenya's grandmother Maphuthi Sekgala said she been teased about her masculine appearance since the day she joined the village soccer team as the only girl.
Sekgala, 80, said: "I know she's a woman. I raised her myself."
When global speculation began mounting over Semenya's gender earlier this week, she rang from Berlin, where she was competing, to speak to her grandmother in the village of Fairlie, near Polokwane in Limpopo province.
Describing the conversation on Monday night, Sekgala told South Africa's Times newspaper: "She called me after the heats and told me that they think she's a man. What can I do when they call her a man, when she's really not a man? It is God who made her look that way."
But Semenya has a thick skin after coping with years of taunting from other pupils at school.
Sekgala added: "If the teasing hurt her, she kept the hurt to herself and didn't show what she was feeling."
Controvercy ... Semenya wore boys' uniform at school and played soccer
Semenya's sister Nkele, 16, also defended her legitimacy as a female and said: "People must stop calling her a man because we are proud of her."
The athlete's best friend Deborah Morolong, 22, said she never had any interest in boyfriends but refused to accept thatshe was not female.
Morolong, 22, who attended Nthema High School in Fairlie with Semenya, said: "She never had a boyfriend. She doesn't like boys. I think they are saying that out of jealousy. It really hurts me when they say that about her."
Meanwhile Semenya's former headmaster said he was "very, very proud" of the dedicated runner, but admitted she reached grade 11 before he realised she was a girl.
Eric Modiba, head of the Nthema Secondary School, from where Semenya graduated last year, added: "She was always rough and played with the boys. She liked soccer and she wore pants to school. She never wore a dress. It was only in Grade 11 that I realised she's a girl."
In an interview with South Africa's Beeld newspaper, Modiba explained that Semenya wore the male version of the uniform at school - the yellow shirts and grey pants. All the other girls wear reddish-brown skirts and yellow shirts.
Semenya was banned from speaking to the media following her sensational final race.
She was whisked away from the crowd within moments of claiming gold with an impressive 1.55:45 time, beating defending champion Janeth Jepkosgei of Kenya into second place and leaving British star Jennifer Meadows to collect bronze.