I am sorry to hear you are worried about Fiona. I am a veterinarian, and will do my best to help.
Is she eating and drinking since this change in her? Did they do any tests at all at the emergency clinic: blood tests, blood pressure, vision test, look into her ears with a scope? Did she have a fever when they took her temperature?
Confusion, walking in circles, lethargy all sound like something is affecting her brain. This could be from a stroke, high blood pressure, a brain tumor, or an infection of her brain (bacterial, viral, parasite). An ear infection
could cause an infection of the inner ear and brain.
If I could, I would begin by seeing if she can see (drop a cotton ball in front of her and see if she watches it fall), take her temperature (normal is between 101 and 102) and try to get a good look in her ears ( although with an inner ear infection, the outer ear can appear normal). I would take her blood pressure, and test her reflexes.
If she has a temp over 104, I would start antibiotics. If her blood pressure is high, I would start blood pressure medication.
If everything I checked with my exam was normal, then unfortunately the next step is trying to image the brain: CT or MRI and these are expensive tests.
Let me know what else I can answer or help with.