Watch the crop again tomorrow to make sure that it has emptied. You can give her some coconut oil chilled and cut into small chunks to offer to her to peck up to a tsp daily. Mareks which can affect most of your chickens, can cause problems with immunity to common diseases. It sounds like she may have a respiratory disease. Those in chickens are usually lifelong, and can affect their overall health and egg laying. If the crop feels hard or doughy, you can massage it several time sa day.