Neurosis is a good possibility especially with the breed, since Silkies and their mixes and derivatives have a very high incidence of mental disorders compared to many other breeds, particularly nervous anxiety and neurotic behavior patterns.
Is she bored maybe? Does she get to interact daily with other poultry, free range, or at least have a decent sized cage if not?
One thing to consider is that just because you're feeding an animal something, does not mean it's actually receiving that nutrient; many chooks lack complete digestive capacity and fail to synthesize one or more vitamins in the quantity they require. This is a great contributor to neurotic behavior. The fact that she eats her own poop makes this a likely diagnosis, since if she isn't synthesizing her food correctly a large quantity of protein would remain undigested or partially digested, making her poop higher value as food than a healthier bird's poop. If flies pay extra attention to her poop as compared to another chicken's poop, you can probably assume she's not processing her feed properly, but even if they don't it's still a good bet.
Another issue is that most feeds marketed as 'complete' feed are in fact base-level survival rations, designed to keep a bird alive and producing for a maximum of two years before it's culled and replaced. Beyond this they die from malnutrition disorders, usually, if not culled; malnutrition can masquerade as health and can take many years to kill.
Meat has far more than just protein in it; she may be needing any one or several things of a whole spectrum of meat's constituents. She may need more essential oils/fats, or probiotics, or fibre, or gelatin, or salt, or any one of many other things. I would review her diet, since even if she is neurotic, many neuroses are due to damage or dietary deficiency and can be corrected thereby. She may still be protein deficient despite the eggs, but I think it's more likely she's needing something that's present in meat but is in lower quantity than she requires.
Just for a start, in order to eliminate as much as possible the possibility of nutritional deficiency, I would give her a pinch of powdered or granulated dried kelp daily with her food. This is a complete mineral and vitamin spectrum source and will assist everything from feather strength to moulting to laying to intelligence to her endocrine system.
Best wishes.