Can you post a video of her walking and some pictures of her legs and feet. I would also feel along her injured for any breaks.
It sounds like a leg injury so far. You will want to keep the Cayuga contained in a small area to let her heal. You will want to give her baths in deep water to help her leg strengthen with less stress on it. It will also take the weight off it and let her relax it.
Look for swelling on the leg and heat radiating off the injured leg. Epsom salt compresses can help reduce the swelling.
You will want to monitor how much she eats and drinks. Some ducks stop eating during an injury and end up requiring tube feeding. If you don't have the supplies I would recommend just having them on hand in case you ever need them. Some of the supplies can be difficult to find and require ordering online.
Depending on how injured the leg is, depends on how long it will take to recover. A minor limp, they can be back on their feet a week or so. And others can take weeks.