Hello Elly, welcome to the Hen House
Is her tail down? I'm guessing she has her head tucked right into her neck and is looking sorry for herself?
Firstly, how long have you been keeping hens? There are some things that new hen keepers don't have experience of and therefore it can scare when bad things happen.
Is she in lay? if so, when did she last lay an egg?
Are your other hens OK?
When did you last worm them and check them for lice?
There are lots more questions that can, and will probably need to be asked so that we can help you but that is enough from me just now.
P.S. Please be prepared to take her to the vets if she gets worse; at the best they may be able to cure her, at worst they could put her out of her misery
![Sad :(](https://chat.allotment-garden.org/Smileys/green/sad.gif)