Hello J.,
I don't have much info, but 2 things: 1) It is typical for menstruation to begin sporadically, i.e. not at regular monthly intervals, and not in full force at the beginning. 2) I have read that the hormones fed to cows and other animals by commercial meat and dairy producers (factory farms) to increase their production and profits get passed on to people when we eat the meat, drink the milk, etc., and that this has been one possible cause of earlier onset of menstruation in girls. I couldn't say whether this is a factor for your daughter (I am not assuming it is) but if she eats regular commercial meat and dairy you might check it out. Good luck with the talk! My kids are still toddlers and it's good to get a sense from this web community of all the issues out there around the bend!