I just saw this thread. I have raised Langshans in the past and your hen looks just like one. The shape of her head and face, u shaped back, tail feathers, feathered feet all look correct.
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That looks just like the bantam Langshan that was sold to me as a Bantam Cochin. Langshan's have the dark eyes and legs and upturned tail with less feet feathering than a cochin. Cochins have yellow legs and eyes. I love this beautiful breed!