Welcome to BYC!
Sorry about your hen. When they get to the point of not eating or drinking with a crop full, generally they are on their way out. Is the crop soft and squishy? You might try to vomit her to clear out her crop. Take her outside and hold her like a football in one arm, support her crop with the other hand. Lean forward, beak completely down, tail up. Gently squeeze and work the crop. The SECOND fluid starts to come up, count to 2 or 3 and stand back up and let her catch her breath. No longer or she can breath is in. You can repeat this a few times until you get most of it out.
If the crop is hard like a ball, this is requires a different treatment of water water and more water. No food for 24 hours, just water and a lot of it.
I would keep her confined away from the others and keep her warm at night. Feed her what ever she will eat, no matter what it is as long as it is soft foods. I would put some probiotics in her water or some apple cider vinegar. 3/4 teaspoon in a quart plastic waterer only. Change it and make new daily. Don't feed her anything but very soft easy to digest foods. No seeds, grains, foliage, etc... If she starts to get better, I would vomit her each morning. Once a day to clear out the gunk. No free ranging, watch what she eats and keep her warm with heat.
BUT...I would post this in our emergency section for more help with this..
https://www.backyardchickens.com/f/10/emergencies-diseases-injuries-and-cures
Good luck and I hope she makes a complete recovery.