At this point, I would check to see if her foot or leg feels especially warm compared to the other. I would get some ointment, like T Relief, that is anti-inflammatory. I would add a half a teaspoon of turmeric to the food daily (be careful it stains) as it is mildly anti-inflammatory as well. And watch her. I forgot what your weather is like . . . please bear with me. If there is much ice and cold ground, sometimes joints will react to that in people, and I reckon it could be the same with ducks.
It could be cold related, it could be the bumblefoot may be trying to make a comeback. If you can stay ahead of it, she should be okay . . . But without being there, and since I am not a duck vet, I cannot give you 100% diagnosis. And I know that's not what you expect. I wish I could, though.