Hi
I have a bantam pekin with the same problem. It has just taken me 2 weeks to bring her back from the edge of darkness. I really thought I was going to have to cull her at one stage as her digestive system was grinding to a halt and her crop was massive and tipping her over with it's weight and like your hen, her keel bone was so pronounced it was like a knife edge with no breast muscle to pad it out and her comb was dry and shrivelled. My girl was still active and ravenous for food but it was just collecting in her crop and not going down. She didn't have sour crop as she was keen to eat and there was no sour smell and despite many attempts to vomit her, I could not get anything back up. Mostly it felt reasonably soft but was just huge and she was clearly starving because the food was not going through her system. From getting her in April, she had always loved grass and binged on it...I think perhaps she had not had access to it before.... and became impacted.
In the end I had to isolate her in a small coop with no access to any bedding or grass (she was so hungry she even ate the tiny scattering of saw dust I put down, so I had to stop that as well. I gave her 4 tiny sloppy feeds a day, made by mixing her pellets with warm water and letting them soak and become mush and then adding a little olive oil and 4 crop massages a day. She also had access to grit and water but nothing else. Thankfully there was still a little bit of poop coming out which gave me hope that her gizzard wasn't impacted. I felt terrible limiting her food when she was starving but she already had so much in her crop and it was just stretching further and further the more she ate. Thankfully, after about a week of small wet feeds and pretty intensive massages, it started to go down and one morning I found that it was down to a lump the size of a golf ball that felt almost like clay, whereas previously it had been soft and squishy. It took quite a bit of massage to get that final bit broken up but thankfully she is now well and back with the flock. She will probably always suffer with a pendulous crop now because it has been stretched beyond it's elastic limit and once she is finished moulting I intend to fit her with a crop bra to help support it and stop food from collecting in the saggy bit and causing another blockage.
I hope my experience is of help to you and your chicken. I would definitely encourage you to isolate her (it helps to be able to see what her poop looks like and how much she is passing) and restrict access to dry food, grass and bedding and massage lots.
Good luck with her.
Barbara
