Is it possible that 450g was just after a meal and 430g was long after digesting/pooping? Not eating for two weeks in the winter is not a big deal if you can explain a rapid 20g loss (by way of feces), however if she continues to lose at that rate you have another issue on your hands (e.g., parasites).

My prediction is that she plateaus and doesn't lose much more and starts eating again in a few months