There are cases where EYP can be treated successfully if tackled early enough and also the age of the hen helps if she's on the younger side. Your hen is lucky you were on the ball for her.Just curious if your hen made it?? I just saw this while searching, as we are dealing with the same thing right now with our Buckeye hen...
Our little Penny had started sleeping in the nest box at night, which at first I didn't think much of as she discovered that it's nice and warm in there when she molted in the winter, so now she sometimes sleeps there on cold nights. But after a few days, I noticed she was acting weird in the morning - not eating much, moving slowly, etc. That was when I picked her up and felt her lower belly and found it puffy and swollen. :-( I knew what that meant, as her sister died about a year ago from peritonitis, so I expected her to go quickly. (Henny died within 24 hours of acting sick, so she must have been septic.)
However, Penny hung in there, and I gave her extra vitamins and garlic for a few days while I was waiting for antibiotics (Aqua-Mox) to arrive from Tractor Supply online. She would come out and eat a little, but mostly only kitchen scraps - no feed, and while she would come out to scratch with the others for a few minutes in the evenings when we let them out of the run, she would soon retire to the nest box again.
She has now been on the antibiotics (250mg every morning) for 1 week, and is back to acting totally normal! She's eating normally, scratching, and back to roosting with the others most nights. Her stomach feels pretty much back to normal (I can't tell if it's 100% yet, and she has a VERY fluffy butt, so it's hard to feel sometimes, but it's definitely WAY less swollen than it was). I'm going to continue the antibiotics for a full 10 days based on things I have read from others on this forum, and my fingers are crossed!!
I know people have said it tends to come back, but I'm trying to be hopeful...
Also, just a tip for others trying to give antibiotics (or other meds) to chickens: I have found that mixing the contents of the capsule with a spoonful or two of cooked rice or oatmeal works amazingly well. Even when they're off their feed, they generally gobble it up in seconds like it's candy! And that way you don't have to worry about it settling in water or them not drinking it all, and it's much less traumatic for everyone than trying to cram a pill down their throat.
I hope your Ruby made it through!
As for giving antibiotics in pill form, it need not be stressful, mainly for the human who mistakenly worries the hen will choke on a pill or be stressed by prying open the beak.
Putting the intact dose inside the beak of the patient insures she gets the correct dose. Mixing it in water or food, while reducing the inconvenience to the hen, risks not getting the full dose into her. Chickens do not sweat swallowing objects that will choke their humans. They have no teeth for a reason. They do not need to chew their food as the first stage of digestion as humans need to do. Their digestion doesn't start until food reaches their crop and gizzard.