pretty similar to some other suggestions. It is easy to make your dog stop growling when food is about. When you put the food down make sure your dog is sitting and waiting patiently, then as she approaches the food you will stand between her and the food and gradually creep towards her making her back away (showing her that you are the pack leader and that the food is your possession), the step away from the food and repeat this step if she goes for the food again.
You then have to get a broom, while she is eating push the broom close to the food, if she goes for it then do not withdraw, hold it there until she realises that she will not win and backs down, you cant use your hands because if she bites you will automatically withdraw your hand, hence the exercise of dominance is defeated as you have backed down. You must do this repeatedly until she does not react to the broom approaching the food. One more thing, have patience.