I had a pup with Hydrocephalus. There are different degrees of severity of this illness. My little one had a severe case, and she was very young. Unfortunately, she had a rough start with a bad breeder....long story, but the short of it is that she would have had a better chance if she had been treated sooner. Is she eating okay for you? Getting her to drink water is important, as it helps with the fluid build-up on the brain. Sometimes vets will also prescribe diuretics to help with this. There is a procedure that can be done where they put a shunt in to help drain the excess fluid, but that would depend on the severity.
It's important to keep them in a quiet environment, as noise can affect them. My little Lily would get very upset if there was too much noise. She would cry and scream, it was heartbreaking. She also started to have seizures, and this was just too much for her little body to handle.
I would sit down with the vet and discuss in detail what your treatment options are, what your puppy's chances are, and how severe her case is. I'm not trying to scare you or discourage you, but these puppies need alot of extra care, and it can be very costly.
Have you contacted the breeder to let them know about this?
We have a member here whose baby has Hydrocephalus, and she was so helpful to me when I was dealing with this. I will PM her to let her know about your post. Maybe she can help offer suggestions.
I wish the very best for you and your little one.