I don't know exactly what is wrong with your girl exactly, but we just went through this with one of our. Thelma was running around and eating also until one morning, we noticed that she was lethargic and not running everywhere like she normally does. We feared an impacted crop also and did exactly what you are doing. She did regurgitate large amounts of water (she was drinking a lot), but not much of anything else. Her crop was also huge. It was not hard but, actually felt "squishy".
I finally gave in and took her to a vet who did an x-ray. Other than a small amount of grit in the crop, there did not appear to be anything else of substance in there. What the vet saw was gas bubbles. Really big gas bubbles !! The diagnosis was candida. She gave her an injection, mostly for pain and inflammation and started her on an anti-fungal drug called Sporanax (Itraconzaole) and also Reglan Oil (Metoclopramide) which a helps prevent reflux and improves bowel motility.
Thelma improved within a day and within 3 days was back to normal, or what passes for normal for this one crazy hen. Her crop remains normal after about 10 days now. The drugs were not real expensive, $22.00 for the Sporanax (the vet gave us extra) and $14.00 for the oil (extra doses there too).
I don't know if this will help you. Your girl may indeed have an impacted crop. Merck's Veterinary Manual gives this as a treatment:
"Improving sanitation and minimizing antibiotic use in poultry help reduce the incidence of candidiasis. Affected birds can be treated with copper sulfate at 0.5 mg/L of drinking water, or 0.5 mg copper sulfate per kg of feed. Vinegar is used as a treatment for candidiasis at 15 mL/L of drinking water. Chlorhexidine is used for prevention or treatment at 2.5 mL/L of drinking water. Chlorine bleach at 0.1 mL/L of drinking water may help control the infection. All of these treatments lack FDA approval."
Good luck ! I hope she gets better.