I had my period when I was 9 yrs. Please talk to her about this openly and teach her candidly about her body and sex. At this age her peers are not on the same page with her and if she knows what to expect it will be much easier. She will develop breasts and underarm/pubic hair before her peers as well. The more she can prepare and the more she knows the better she will feel and the less embarrassment she will feel.
It doesn't sound unusually early to me, though you say it's unusual in your family. I was 12 when I had my first period, and that was a generation ago, and people do say kids are maturing faster now because of better health and nutrition, and possibly because of the prevalence of hormones in the food chain. Get her pads with wings, and all of the sizes of tampons that have cardboard applicators -- from "lite" (or "junior") to "super," -- and show her the products and tell her the differences. She should try the narrowest-size tampons, and if she can get them in and they feel OK, she could wear one with a pad. That will give her some idea of how absorbent they are and how often she should change them. If she doesn't prefer tampons, she should just go to pads. Her sisters should be able to help too, they can give advice that moms can't. You might also get a tube of sterile lubricant, such as KY jelly, so she can put a dab of it on the outside of the tampon applicator for the first few tries.
oh your little girl is becoming a woman early,sound like she is mature for her age..just talk to her about the birds and the bees..and how to keep track of her cycle, teach her how the cycle works..and give her strong motherly advice..she has sisters so that helps a lot too..and tell her happy woman hood early..bye..
It does seem early but one hears that they are maturing faster than in the past, is she heavier than your others? sometimes weight affects their maturity, Its okay its a sign she is growing up fast and we don't always want them to , just handle it as you did your others. If she doesn't mind all is okay, it may be spasmodic to start with and spotty, I guess she already knew about it .good luck