We will need a bit more info to help you. Do you know when she last laid? How does her crop feel? Empty, hard, soft and squishy, etc.? What do droppings look like? Does her abdomen feel bloated at all (between legs, below vent), very hard, or water balloon like? Any discharge from nares or beak? Look inside beak to see if it's normal. Any wheezing or other respiratory symptoms? Check her over thoroughly for any wounds or injuries (if any are found pictures help), check for mites or lice. I would isolate her until you get it narrowed down a bit, that will also give you a better chance to observe droppings and such, and she does need to be kept warm if she's ill. Where are you, generally, in the world? That helps sometimes in suggesting things. What do you feed, including treats, and how are they housed? Free range or enclosed run? The more detail you can give the better others can help.
