i would think that too but she came to me that way, i got a pair of them and the other one is fine, I'm concerned about it being something more. i felt around her pelvis and there is a mass that feels allot like an egg, but again the bird fits in one hand so i know she is too young to lay eggs.
Are you absolutely sure she is only 3 months old, maybe she is a bantam at Point of Laying? Pictures would go a long way. Both of the vent issue and of full body close up with comb and wattles in the pic.
Well not a bantam. I don't know with the vent issue. Sounds like cocci but no blood. I would get some Corid and treat for that. Also keep bumping the post every 30 min or so and hopefully someone has dealt with this issue will help out.
Try soaking her in a tub of warm water. This will relax her. Hopefully some of the warm water will also clean out her vent. Separate her in her own cage and make sure she only eats her grower feed and clean water. Put a big dose of Apple Cider Vinegar in the water.
Then, time will tell. If she is to improve, she will. But if this is an internal ascites issue, there is nothing you can do and unfortunately, you'll likely lose her. Check back with me in two days, after you've done what I have outline above. Time will tell.
I PM'ed a BYC Educator and this is what he suggested. Hope this helps your girl.