With coccidiosis, you may see blood in the poop, but not necessarily at the vent, and you probably won't see anything like that. When the last bit of intestine moves to the outside, it is called prolapse. It's probably more common after they start laying. At her age, she may have something internal wrong that you won't be able to do anything about. The only thing I can think of that might be treatable is constipation. Be sure they always have access to fresh water. If she is at the low wnd of the pecking water, the others could be making it difficult for her to get to the water, and it might help to give them another waterer, in a different location. A small amoutn of molasses n the water will act as a laxative. Some would probably use epsom or ACV.
You will most likely have to separate her til she is healed, or the others will peck her and literally eat her. It's even possible this started with some sort of wound which was made worse by pecking.
Maybe some other people will have some other ideas for you. I hope things turn out well!
