It sounds like it might be a case of prolapse or bound egg. My leghorn had her bottom *fall out* so to speak. She would try to poop and instead would make chitting noises and puff up her feathers. It took a little over a week of us giving her a bath and cleaning out her backside and pushing it back in. It got pretty bad with her and we had to separate her and make sure she ate and drank. We started with honey after reading up on BYC about what to do but I was not pleased with the results so after about 4 days of cleaning her out with little results we changed it up a bit. Her insides had been out so long they had dried up, so we pulled off the feces and scabs, pushed her backside back in and swabbed her up with aquaphor, a water based gel to keep her backside moist. After about 3 days of this she was better and about 7 days later was back to laying.
I have to say it was a lot of work and I am not sure I would recommend it for every backyard enthusiast but would say it is worth a try. Some would say cull as it was nearly 10 days of treating her and she was a $4 chicken to start with but I did it so I was familiar with it and knew what to do. If it were to happen to another one of my chickens that was not so dear to me and the case was as severe as my leghorns I would probably cull her to end her pain because she was in a lot of discomfort for about 6 days.
If she is egg bound there are many post here on BYC about possible ways to treat it. I have not dealt with this scenario myself so have little in the way of advice to give on the matter. G'luck and hope all goes well.