Hello and thank you for using this site to help you. There are over the counter products such as Distaste and Deter , you did not mention that you tried. Adding some pure canned pumpkin to the diet works for some as well.
She may still grow out of it as she is very young in dog terms. much depends on where she came from, meaning where she was bred and raised originally, before you got her.
Coprophagia is pretty common in dogs, it's a combination of natural instinct and a learned behavior , because pups see the mom eat their stool when young to keep predators at bay. As well, in dogs from poor breeding grounds, meaning that the breeder is not picking up after them immediately, or they are puppy mill dogs, it becomes a food source.
Sometimes bulking up the regular dog food with the canned pumpkin helps if the dog sees the stool as a food source.
The only other way to keep a dog from eating its stool is to have someone come over and walk the dog to get in a routine of going outside and to an area the dog won't have access to it afterward.
Sometimes crating the dog can help as dogs do not usually like to eliminate where they sleep or eat so putting food and water in the crate can help. She is old enough to hold her eliminations for 7 to 8 hours.
You can read more on coprophagia here, but I do think your dog is still young and will eventually grow out of it.