Circling combined with a seizure can indicate hydrocephalus as you say. It is also a symptom of a liver shunt. Definitely take her to your vet and make sure she has a bile acids test to check her liver function. Yorkies are thirty-six times more likely to have a liver shunt than all other breeds combined so you must rule that out.
Does she have any other symptoms of a shunt?
What are the clinical signs of a liver shunt?
Clinical signs are often seen at a young age and include small stature, poor muscle development, behavioral abnormalities (circling, disorientation, unresponsiveness, staring into space, head pressing), seizures, and quiet demeanor. Other less common signs include drinking or urinating too much, apparent blindness, diarrhea, and vomiting. In some animals the signs are associated with eating protein. Other animals are diagnosed when they take a long time recovering from anesthestics (i.e. barbiturates) or sedatives (i.e. acepromazine). Some animals show no signs until they are older, when they develop bladder and kidney infections and stones. Diagnosis of Portosystemic Shunts