Lame duck

Unless he is twice her size/different breed he would not have done that much damage. She will need rest away from his advances and check her over for any signs of leg weakness or faeces abnormalities. Give her a wash up bowl of water to herself that she can get in and out of easily on her own and check she is eating ok.

im guessing the mating took place on land and not water which gave his full weight on her, how many ducks and drakes do you have, it sounds like he will need keeping away from her or add more ducks for him.

I had the same with one of my araucana hens. So I seperated her for a good month to give her time to recover (I let her roam out of the enclosed run when I was there and able to stop the boys getting to her). She had her best mate sleeping with her so wasn't lonely. Now I have got rid of my large fowl boys so all is well  .