She needs to see a vet asap. When you picked her up, she most likely had a bad case of whips or coccidia, left untreated, both of these can be fatal conditions eventually. I would get a fecal tested immediately and rule that out before you go jumping to blood work and other screening procedures. She'll still likely need an IV and concentrated treatment, but I'd for whips/coccidia before dumping loads of money into your vets hands.