Bella eats her poop...sometimes while its still coming out

EWE! It is so disgusting!!! Anyhow; I have spent over 100 dollars on products in pet stores and the vet's office. Nothing works. They told me the food she eats is too rich and she still asumes it's food. I have tried changing her food that doesnt work either. She has been tested for al sorts of things; nothing wrong. Just a poop eater. I here that they do out grow it sometimes...I hope she outgrows this!