Sounds like you need to treat to coccidiosis and NOW! Please go to the emergency/disease forum and post. If you have any Corid, or Sulmet, start dosing, and treat the whole flock. You might lose the one you're working on now, but hopefully will save the rest of the flock if you treat soon.
To get a chicken to open their beak, gently pull down on the wattles, and they'll open up. Be VERY carefull trying to give it liquids though. You can get it into the lungs very easily and she'll have pneumonia then, which could kill her. Easier to make little balls (think pea size) of the Corid and her feed and put those in the beak and let her swallow on her own. You can also use a syringe, eye dropper, med dropper, and drop the liquid a drop at a time onto the top of the beak. When it falls to the beak end and down the sides, they'll usually drink it. You can also try dipping the beak into liquid like you do a small chick.
Most important though seems to be treating the cocci, and then working on that impacted or sour crop.
Does she have any odor coming from the beak area? A sour smell? Has the crop been this way all day? In the morning, the crop should be empty if all is working OK. Like any animal or human though, when they are sick, they don't want to eat, and the digestive system slows down.
Have they been wormed? If so, when? I wouldn't treat the cocci and worming at the same time, as it would be harsh to their system. Two weeks in between treatments should be OK though.