Unfortunately I have to agree with Wyorp Rock. The likelihood is that a mass in her abdomen is constricting her gut and backing her up resulting in her crop being slow. Feel around her vent and between her legs and compare to one of your other hens. There was another thread here on BYC recently where a lady had the same problem with her hen. After a significant vets bill she made the decision to euthanize the bird and her husband opened up the hen and found her oviduct was packed solid with "Lash eggs" which are a mixture of puss and egg material caused by an infection. You may be able to feel something similar if you insert a lubed gloved finger into your chicken's vent. That might help you make the difficult decision. If she has an infection of the oviduct (salpingitis) and isalso packed with "lash eggs" then there really is no hope.
I will post a link to that thread so that you can read it and see if it sounds similar
https://www.backyardchickens.com/threads/eggbound-after-sour-crop-euthanize.1207070/
I will post a link to that thread so that you can read it and see if it sounds similar
https://www.backyardchickens.com/threads/eggbound-after-sour-crop-euthanize.1207070/