Good Morning and Relax.
My thoughts, the shavings you are from a larger piece that is being ground up in her gizzard. This is how birds take in larger chunks of nuts, hard food, etc and process it into smaller pieces that will pass through the digestive tract. You might want to get some slippery elm powder at the health food store and mix it (1 part water/ 4 parts SE), and feed it to Kita to help anything larger pass. Nut shells can only be processed to smaller pieces and will not be digested like the nut meats. You vet may suggest and X-ray to see if there might be an obstruction. I have seen small pieces of wood in the poop of ours on a rare occasion, checked them under the microscope. Hard shells and wood are not food and will not be totally digested!
Have to say checking your birds poop is commendable and a great way to monitor their health.
Gary