"But she's settling in really well, and doesn't seem to realise that she's different from all the other chicks." Good grief. I'd actually be extremely sceptical. The bird looks like a chicken; sometimes they have extra bits.
Sadly we never got to eat any of the Pheasantams because they tended not to live very long. I suspect someone else ate one or two of those which did survive a bit longer, but very rudely gave no feedback (or feed back).