What exactly does she eat every day including treats and feed? Does she have any other symptoms? Crop problems can accompany other illnesses which slow things down. There also can be blockage lower down in the GI tract. Tumors can form in the crop from viral diseases such as Mareks and others.
Two Crows knows a lot about crop problems, and some use crop bound capsules, which basically are stool softeners, such as doccusate sodium (Colace.) The dosage is two (I would open them.) Some also use acidified copper sulfate 1/4 tsp per gallon of water for a couple of days. If feeding her whole grains, stop, and use soft foods such as plain yogurt, egg, and watery feed. You might even want to withhold her food for one day, and give only water with electrolytes and vitamins, massage it often, then see if it empties.
Here are some links that might help:
https://www.backyardchickens.com/a/impacted-slow-and-sour-crops-prevention-and-treatments
http://www.the-chicken-chick.com/2012/04/answers-from-chicken-vet-on-impacted.html
http://www.chickenvet.co.uk/health-and-common-diseases/digestive-problems/index.aspx
http://www.tillysnest.com/2012/01/crop-issues-html/
