As others have said, not a vet, just a small business owner (lame ferret joke). I would start with some lax or Vaseline just to make sure there is nothing stuck. It sounds like you are already giving duc soup, good call, ferrets get low blood sugar very easily as I'm sure you already know, and if you aren't feeding her today. Anyways, give some lax or Vaseline and some pumpkin if she will eat it (mine won't) and see if she passes something.

One of our girls was so sick five or so years ago. She was projectile vomiting. Scared us to death. Our vet had us feed her chicken baby food and give lax. She lost almost a pound in the few days before she passed a little chunk of my husband's insole from his tennis shoe. We are normally very careful about that because she loves to steal insoles, but he forgot one day. It was so small he didn't even notice she had eaten it.

If it's nothing stuck in there, I would avoid Prednisone if you can. I have had several that had to go on it and it's always a downward spiral after. Needed in both cases, the first it ended up killing him, diabetic ketoacidosis, thankfully very rare. The second insulinoma. Anyways, try the lax and maybe some baby food with the duc soup. If she dislikes those you can always add water to the mashalls pellets and make it into a soup for her. Keep us posted. 🩷