Awwww.....I bet Hailey knows all about being cooped up in the pen so she feels her pain.

I think giving her straight nutri drench was a good choice. Wastes less too. I bet it wouldn’t hurt to do a couple treatments like that. Most vitamins are excreted through the urine if not needed. I’m sure if you gave it straight to her 365 days a year, it would be too much but a couple days would be fine.
One silly thought, if she doesn’t keep getting better, do you know of anyone with a metal detector? Could you run it over her to see if it beeps quite a bit?

If it does then you will know she’s likely ingested some scrap and her getting better is unlikely unless it’s small enough to pass. I know it’s a long shot and hopefully she continues to improve.