Sorry you (and her) are facing this.
How long has she been "off"? Is she pooping? Not common in first time layers but are you able to check for egg binding?
Here is a link with all the state poultry labs contact info listed for quick reference but doesn't include most website links..
https://www.metzerfarms.com/poultry-labs.html
I could provide more direct information links if you wish , but need to know which state you're in. Adding you general location to your profile can help folks make their best suggestion possible at a glance... re weather and disease outbreak type information and also sometimes knowing what resources are available since many on here are in other countries.
Is veterinary care an option, to help see if there is a foreign object and maybe verify or rule out any possibility of gape, coccidiosis, etc?
I wonder if
@Eggcessive,
@Wyorp Rock,
@azygous,
@casportpony have other clues or considerations I haven't mentioned. TIA for looking and also sharing if so!