She didn't kick her, she ran over her, horse legs, horse hooves, duck, feather, it was all a big blur.
And I agree, I thought for sure she wouldn't live. Thanks so most for your honest reply.
Thanks everyone for the wonderful advice and support! I am happy to report that the duck made a complete recovery and did not sustain and noticeable injuries.
I did the exact same thing once and decided to raise my duckling with the chicks. If you decide not to put it in with the chicks you might want to look at how these people used heating pads for their chicks and ducklings...