Just wanted to make sure your dosing was correct, and it is. For the oral dose mix 1/2 tsp powder with 2 tsp of water and give her .34 ml of that per pound of her weight once a day for up to three days, or if she's small give .07 ml per 100 grams of her weight. If you give a bit more it won't hurt her. Then if she's still not drinking well you can give her some of the regular medicated water carefully by syringe also periodically during the day. For her age and symptoms I would also have started treatment for coccidiosis, that is the most common illness in young birds and chicks, and it won't hurt her in the event it did turn out to be something else. Depending on the strain, and how numerous the coccidia, the time for her to start looking better can vary. Try giving her some chopped up scrambled or cooked egg to see if she'll eat that.
Also, just to rule other things out, keep an eye on her droppings to see how they look, and check her crop function, make sure it's empty completely in the morning before she eats. I usually see some improvement within 48 hours, but it can take longer to really look good. If she still doesn't look improved by tomorrow, and a vet is an option, then I would do that. But the Corid will do no harm in the interim.
