Is she able to apply any weight to the foot?
If you gently palpate and bend the leg do you feel any broken bones, or hear any cracking/popping?
If you say yes to both of the last questions, I would suggest taking her to a veterinarian, but if you do not feel any broken bones it is likely she received some soft tissue damage (sprains, strains) which can occur due to over mating, by tripping, or by getting their feet caught in objects (wire, rope, twine, etc).
The prognosis for these injures is very good and most birds will recover after a week or two. To enhance the healing process, you may try an limit her movement for the proceeding week to help reduce further reinjury of the area. Letting her swim in cool water daily, occasionally with the addition of Epsom salts will help at reducing some of the inflammation. NSAIDs, such as aspirin, carprofen, and meloxicam can be used to help reduce inflammation. The aspirin dose in birds is 5mg per kilogram of weight.