Have you checked inside her beak and back of the throat for any unusual yellow cheesy growths or white spots? Use a flashlight to check. One really can't say what is wrong. Can you get a handraising formula for parrots from a petshop? Mix the powder with a bit of water to form a soft clay. Then make small peasized balls and handfeed to her. This will be more nutritious than peas. Peas have lots of moisture, so that can explain why she is not drinking much.
Put her seeds in a deep bowl, easier for her to pick up. See if her droppings improve on the formula balls.