I agree with you about it not being Cocci- yeah, she would be dead. I had a hen die from that and it was less than 24 hours- gone so fast. I really was surprised how fast it could take a poor animal.
Is she eating now? I'd get some food in her. I was told that you tube feed a chicken and they have not been eating that you should always start with tube feeding water first. (I don't remember how much, but I'd assume at least 20 to 30 cc's- I think they are called. ....the measured notches on the huge needle-less syringe) If she is super skinny and not doing so well, i wouldn't worm her now either but at least get food in (and out of the backside) to make sure the digestive system is up and running ok first. I'd give her about 2 or 3 days of tube feeding before I'd use the worm medicines, but that is just me- not any solid advice, just a guess. As you said, she could be too weak to handle it. It is possible it could be worms. I'd use safegaurd or valbazen.
Oh, the stuff I used to tube feed her was a Baby Parrot Formula - the company is called Exact- You mix it with warm water (not hot as this may burn the crop) Instructions are on the bottle, but you will need to feed more to a large chicken than what they recommend. I don't know if you are near any Pet Smart stores- but this is where I bought my batch. In fact, I always keep some on hand for emergency tube feeding. The small 'tub' of this stuff costs about $20, but it will last a few weeks or so, I'd think.
.. It is really easy not to notice a bird getting skinny because of all those feathers! You could try blending up the regular feed, but its consistency might not be liquid enough and be too solid to get down the tube. Its worth a try I suppose. Raw egg, yogurt, milk, ... blueberries... anything she will eat is good, just to get some food in her. That's priority number one... well, other than just tube feeding her water first. (The system won't 'go' or move without hydration, so always give plain water first!)
I don't' know anything penicillin at all. Not sure if that is the best choice. My vet prescribed Baytril, which she told me was a very broad spectrum antibiotic that will help fight many different things. What I learned about medicines is that it has to fight the specific bacterium or what-have-you... so that too is difficult to figure out, meaning the wrong antibiotic may not touch whatever it is that is causing the problem. I'm not sure I would inject her either, being that thin. Again, I know nothing of penicillin, and never worked with it... perhaps ask here on the emergency board? Perhaps someone else could help you from there. I'm sorry, I just don't know anything on that drug. There is also another antibiotic that is sold at
Tractor Supply stores- I think I mentioned it here in this thread of trying it. I can't remember the name, sorry that is not helpful, but its very common- Tetracycline, I think? Comes in a water soluble powder. It might be worth a try to use that.
Oh, the other thing I wanted to note on was that with EYP, you can't drain the belly. I think that is with ascites. Its where fluids accumulate and then can be drained using a needle. With EYP the abdomen will be very firm, hard and rounded not at all gushy or wubbly with, say, acites and fluid retention. All of my hens that had EYP looked as if a very firm ball was lodged in their lower abdomen- the abdomen walls so pushed out at the end you could see the veins. How they die from it is that the internally 'laid' (stuck) eggs accumulate and swell the abdomen and sooner or later the organ walls can split open and the infection gets into the blood or they bleed too profusely internally- or both at the same time. It doesn't sound like your bird has anything like that though... you said she was light to pick up. My my birds had EYP they were skinny everywhere else but their abdomen and they were heavy in that area.
Giving the nutridrench is a great idea. Definitely keep doing that!
Sounds gross but maybe you could post a picture of her poop? Any yellow streaks? Is it green? Small? Any white parts? Is the water bit with a tinge of yellow or green or white? Is it watery or more like gelatinous?
It does sound like the cold weather is affecting her greatly. Its best to bring her in- anywhere- out of the cold when a bird is sick. If the cold has been affecting her in the negative , it probably means the bird's body doesn't have the strength to fight infection
and keep the body warm at the same time. Its too much for her to handle, so she will need the warmth to keep her strength to fight the infection.
You mentioned her being off balance.... sometimes food poisoning can do that- and often an animal will drink large amounts of water if poisoned by something like algae or large amounts of bacteria- you had mentioned she is drinking a lot. Could she have gotten into something she should not have? Anything laying around that could be causing food poisoning?
Anyway, just trying to help surmising what could be done.