i got mine at 10 too. It is actually very early, but a lot of girls who still haven't got it, lie about it sometimes and say that they got it as early as ten. When actually its so much better if you get it when your older. But i bet your friend isn't lying, so don't worry about it.
Yes, my mum actually started when she was 8 and there's this girl, though its a really sad story because she had been abused to make it happen, got pregnant when she was 5. Which means she had to start her period around that time.