Did you check her for a stuck egg? If there is one stuck she may not be able to poop. Vaseline on a latex gloved finger inserted no more than 2 inches...you will feel an egg if there is one there. Is that hard poop inside her vent in the picture? Were you able to clean it out? The only other thing i can think is a partial prolapse when her inards stick out of the vent...you would need to gently push it back in and keep her seperated in a dark place. Hemmeroid cream can be helpful to reduce swelling and you may need to continue to push back inside.
Just one more thought. I had a girl with something sticking from her vent about 1/2 inch once and immediately got her into bath and tried to remove by gently pulling. It became clear fast that it was attached. It was prolapse but had "dried out" and felt like poop not flesh to me. I used loads of vaseline to try to soften it and then an antibiotic cream and eventually antiseptic spray and had to continue to push it back inside over a couple days. She didnt seem to be able to poop until i pushed it in and held there for a bit. Then everytime she pooped it came out again. The piece that had been sticking out was hard and sort of scabbed over. To my surprise she did heal and even resumed laying again. Do you think that may be it?