When a bird is sick you have to start ruling things out if you want to save the bird. Unless you take a bird to a good avian vet and have fecal samples and lab work done anything else is just a guess. Being that this bird is new and is sick I would definitely treat for coccidiosis even if just to rule it out. The treatment certainly does no harm. I would also deworm her. Those are two of the most common and easily treated issues chickens can have. Then you go on from there if there is no improvement. There are all kinds of things this could be but you can start by ruling out the most obvious possibilities and see if she improves or if this is something more serious.
