She is a lovely looking duck, I can see why you are attached !
Its great news that she is responding to the additions to her diet - I suspect if you keep up with the new diet, keep her drinking water very clean (splash of acv might help with that) and keep her bed changed, things will continue...
Hi there - I hope your duck is doing better today. This is a bit late in the day but we had this happen, and like @Duck mommy 2019 we bought the duck inside, we put her in a crate with sawdust, covered the crate with a blanky and put her next to a heatsource.
We took her to the vets the next...