there are two possibilities. either she has to learn to hide her poop in the stray yet or she has parasites like worms or fleas. you should check with a vet. there is medication and it works pretty well and...
ah if she has worms she is eating really well and good - I assume it could be that. But really - it is not much of a hazzle. when we got Nuit she also had worms - it is one pill she has to take and another one