What size rat were you offering? I've found that if I offer a smaller than usual sized meal, they usually take it without much hesitation. For instance, offering weanling rats instead of small/medium size rats. Smaller, and more frequent, meals seems to be working out well for a few of mine who would otherwise be skipping larger meals.
I wouldn't worry if she skips a meal or two here and there. It's all part and parcel of having a ball python. ;)