Some reasons dogs will eat stool include: If they're hungry and there's no food around, if they're suffering from nerves, or some eat it to clean up after themselves.
LIkely just because it is bored and sees something it can chew on. Another reason could be because of a sort of tooth displeasure where they feel the need to chew and gnaw at something to ease the displeasure.
Dogs will eat stool due to nutritional imbalance. The first step in solving this issue would be to take the dog to the veterinarian. The second step might involve upgrading dog food.
she is lacking something in her diet. But there is something you can buy and feed her that will make her stop doing it that way she won't make herself sick.