I would not give her mashed egg shell. If she has an impaction that will just add to it and massaging her crop with egg shells inside it could cause abrasion and inflammation. She does not need calcium because she is not actively laying and even if she did, the layer feed would provide more than enough. Personally, I would get some unmedicated chick crumb because it is higher in protein and mix it with a lot of water and add some Nutri Drench so that it is a sloppy gruel and only feed her that, she will not need water as well if it is very runny. Cage her to prevent her eating anything vegetation wise that will add to the impaction and maybe start giving her some coconut oil to help to grease the wheels so to speak. You also need to check her over for abdominal swelling sometimes slow or sour crops are caused by a blockage lower down the digestive tract often as a result of a reproductive issue. Cup your hand between her legs and feel for any bloat and compare to another healthy chicken..... doing this whilst they are roosting at night is easiest as you can feel adjacent chickens and make a direct comparison.
If it is purely a crop issue, it is often a mass of tangled vegetation that is stuck in the bottom of the crop and will feel mushy. It acts like a sieve, allowing a small amount of liquid and finely processed feed through but holds back anything that has any form and is not easily broken down. It may be long grass or straw or hay and if she has access to vegetation she will often continue to eat it and make things worse. She needs to be in a cage with no edible bedding..... newspaper or puppy pads are probably best. Keep massaging as often as you can and just the very sloppy food that would pass easily through a kitchen sieve and coconut oil. There is no real point in feeding her more until that crop empties properly. If it is still not going down after another couple of days, try a stool softener (without stimulant) like Docusate sodium (Dulcolax).
Sometimes the mass needs to be removed by surgery but that is a last resort. It is important not to let them get too weak before you resort to it though or they may not be strong enough to recover. I can talk you through the surgery if it comes to that. Vets are good but have to use anaesthetic and that can be risky for chickens and of course they are expensive, so if they are not an option and there is no other hope, home surgery can be remarkably successful. The surgery is not complicated, just a bit fiddly and you can stick her back together with super glue rather than have to do sutures but obviously no good if you are squeamish. It is very much a last resort though. My little bantam was up and running around and eating within 10 minutes of gluing her back together and was back up to weight and laid an egg exactly 2 weeks later, so not overly traumatic for them.... just something to consider. I took a soft ball sized tangled mass of soggy straw out of her crop, that clearly was never going to pass down the line or come up.
Good luck with your girl. You might find fermenting the chick crumbs and water helps to keep the crop more healthy whilst she is
Thank yoy
