My 15 year old Irish Setter mix has not eaten since last Wednesday. Had diarrhea, very lethargic, wobbly back end. Husband took her to vet yesterday and got a diagnosis of flu or giardia. Vet gave is pills for diarrhea which she doesn't have anymore because of nothing in her system. Drinks small amounts of water but struggles to get up and move. I'm freaking out because she's my "baby," What could it be -- I can't get her to eat or anything!