maybe talk to her about next time you are having af? idk, mama! i think it depends on your relationship with your dd how you would broach the subject.
the way my mom did it GROSSED me out completely and i had issues for years. unfortunately, i blocked it out and can't quite remember how she did it. i think it started along the lines of " you might start to have 'feeeeeelings' soon" *shudder*. and she always used the words "discharge", smegma and vagina. YUCK.
my dd is 3 and she knows all about yonis, uteruses, fallopian tubes, ovaries, wombs, placentas, uterus-blood etc etc.
we talk about growing up, getting big breasts (nay-nays), growing armpit and yoni hair and getting uterus blood.
it just kind of comes up naturally, i guess.
i honestly wouldn't know how to talk to her about it at the age of 8 if i never had before.
i might plan a special girls day and talk about getting her moon and that we are going to get a special box and supplies for moon-time. i would let her pick out some cool cloth pads in patterns/colors she liked. some special skivvies to wear during moon-time. a journal to write in (talk to her about pms and stress), toni weshclers book for girls, maybe a candle or some yummy soap.
that's what i would do!
hth mama and let us know how it goes!
eta: sometimes she calls it yoni blood, she sometimes says "when i grow up and get yoni blood, then i can be a mama and have babies!" it's a happy thing for her, when she talks about it she's totally stoked.