She could have coccidea which has been rampant this year. However many times the vets can't spot it in the feces. It probably wouldn't hurt to ask about putting her on Albon anyway. Coccidea is like having a stomach flu 24/ 7. And get some A/D from the vet, or baby food as already suggested and make her eat! Get a few puppy sized oral syringes and force her to eat several times a day. A kitten her size can go downhill very quickly if they aren't getting enough nutrients. She may need sub-q fluids too. Poor little infant kitty....purrayers winging in.