Try some food she likes mixed with natural yoghurt, if she wont eat it use a shringe but be careful you dont force it into her lungs.
It has worked a few of my chicks, could be sour crop but I'm no expert none the less worth a try.
I have had over the years similar issues with my chicks, drinking excessive amounts of water and becoming weaker until they stop eating and drinking. The first few I took the vets who prescribed antibiotics but days later they were died. I have now resorted to mixing cereal, (bran flakes, corn...