Since ducks are such flock animals (even more so than chickens), I would recommend putting one of the injured duck's buddies in the cage with her. Since she's injured (versus sick), having a flock mate with her will help keep her more calm. A few years back I had a duck injured in a mink attack (puncture wounds, feathers ripped out, etc). After I cleaned her up with soap and water and applied Neosporin to her wounds, I put her and a buddy into our brooding box in the garage. The brooding box has a heat lamp, clean shavings, food and water in it, and is about 3 foot by 3 foot with a wire cover on it. Normally we use it to raise chicks every year, but it makes an excellent hospital as well. I initially had her in it by herself, but she cried (quacked) non stop and seemed really agitated. When I put a buddy in there with her, she calmed right down and the two of them cuddled up and went to sleep. They stayed in there until her wounds were scabbed over, about two weeks. I also cleaned the shavings daily (since ducks poo a tremendous amount, and obviously you want the wounds to stay clean!)
Also, make sure that whatever enclosure you have her in is fly proof. More of an issue in the summer, but nothing draws fliers quicker than wounds, and that's just gross. When my duck was hurt, I put a scrap of window screen over the hardware cloth cover on the "hospital" box, and that worked great.
