ChicoryBlue
Enabler
If she is "regurgitating" that may be because her crop is too full (tube feeding too much) or she has a blockage somewhere. Have you found a crop issue? How does it feel?
Be slow and careful if you are trying tube feeding. It's really best to get personally trained by a vet or someone who has done it and can walk you through it. I got training by a vet on what the tube feels like on their neck when it's in correct position, and @micstrachan has a very good video with tips on it.
A slow or blocked gizzard is problematic and may not be survivable. I added coconut oil to wet baby bird formula in tube feeding a hen, and she did pass a long very tough fiber that had been in her system for weeks and possibly caused an infection. She appeared to recover and did gain weight after that as I continued with less intensive tube feeding - every few of days - but ultimately passed from unknown causes (cancer I suspect).
For molts that the hen drastically changes her diet - my limited experience (two hens in four years) has been that it's not that they won't eat, but they don't want to eat the same things they used to, like their usual feed. They will eat new things, at least a little of it, before rejecting it. Try baby bird formula (not thick though, it tends to be very gooey for them to try to eat), and seeing if she'll eat salt-free sardines, cooked chicken or beef, dandelion or collard greens. Try a high-protein feed like chick starter. Kaytee Exact formula: https://www.amazon.com/Kaytee-Exact-Hand-Feeding-Birds/dp/B0002DGJH8?th=1
Also, have a friend or two with the hen in question, inside or out. Company is very helpful in healing a sick or injured bird and getting them to act like a normal chicken again. I had a recovering chick/pullet that ate much better when her sisters were eating near her.
Do you have a cooking scale? Weigh your bird to get a clear idea of their weight and any subsequent weight loss or gain. You can gauge the keel-to- muscle ratio and actually tell if they are starving by feel:
