Our 4 yr old tabby female has been lethargic and throwing up for the last 3 days. we have taken her to the vet twice. they xrayed her and ran tests and found nothing. They ran a cbc test, electrolytes, SMAC and found nothing abnormal. She isn't wanting to eat and is still vomiting some bile type fluid. One of our male cats gets near her and hisses. What can be wrong? Her third eyelid is not showing. She seems lethargic and sort of wants to be alone.