not sure if its the same with cats, but I had a dog who did it. Its called Coprophagia and is usually something that a kitten or puppy grows out of. It happens for a variety of reasons, especially 'in the wild' where nutrients can be gleaned second time around and also to attempt to 'hide the evidence' which could lead a predator to their den.
There are tablets that can be put in cat food which will make her poo unpalatable (!) and hopefully stop her. But she should grow out of it soon anyway