THE best thing you can do for your daughter to lessen the effects of PCOS if she is going to develop it, is to make sure you get her on a healthy (not extreme) LC plan, such as the low GI plan. That would be ideal for a developing girl of her age. The reason I say that is that if your daughter does have PCOS, then insulin resistence will almost certainly be there with her - getting her on a low GI plan will minimse the effects of that.
Good luck!