Hi
@villmets 
Welcome To BYC
I'm sorry to hear you hen is sick
Do you have a vet that can perform a fecal float and gram stain for you?
Does your hen have any swelling/bloat or feeling of fluid in the abdomen?
What does her poop look like?
Any photos of the poop and your hen are welcome.
Internal laying/reproductive disorders like Egg Yolk Peritonitis, Ascites, cancer, tumors and Salpingitis are complicated.
The dropping of eggs/egg matter into the abdominal cavity, tumors, cancer, fluid, etc. - any of these conditions are not contagious in and of themselves. My understanding is that the fluid/egg matter are a breeding ground for bacteria, so secondary bacterial infections could be common (like E. Coli, Salmonella, etc.). I'm not a vet or an expert, but my thoughts would be that
it is possible that other birds could pick up bacteria from ingesting contaminated feces and get sick if they are immune compromised or have an underlying illness. Manure management may help minimize this. But let's be straightforward here - chickens scratch in the dirt and ingest all sorts of things (poop, dirt, etc.) daily and usually do fine.
Antibiotics
may help fight any
infection she may have and give her some relief for a time, but they won't cure the underlying condition - in your case - if it's Egg Yolk Peritonitis - then the egg matter will still be in the abdomen festering. I'm not trying to be graphic, but there is no where for it to go and it won't dry up. IF she is full of fluid, then draining the fluid can help give relief for a short period of time as well. The only antibiotics I have seen mentioned when trying to treat internal laying disorders are Tetracyclines and possibly Baytril - if you can't source either of these and you feel that the Penicillin is the only hope, you can try and see if it makes an improvement or gives her any relief.
I wish I had better answers for you - it's heartbreaking to see them struggle with this. Unfortunately, reproductive disorders are common and it's frustrating to not be able to do much for them - I've been there and tried.
Good photos of what type of matter that can be in a hen's abdominal cavity:
https://www.backyardchickens.com/th...-need-of-some-help-and-guidance.853726/page-2 (POST#17)
Internal laying/repro disorders can have very similar symptoms - when a hen is examined upon death you can get a better idea of what was going on - in this case, note she had egg yolks/fluid and some gelatinous (cooked yolk) looking material - this is what festers and causes infection - none of this will dry up even with antibiotics.
View attachment 1119854
Photo taken from this thread:::
https://www.backyardchickens.com/threads/egg-yolk-peritonitis.1154532/#post-18103856 (more photos are on this thread)