Tumor or inner ear infection?

Question
Hello, my poor little rat Greyskull was dragging her head around her cage about a month ago and looking generally miserable, so I took her to the vet. I was sure she had an ear infection, the vet checked and confirmed, and prescribed an antibiotic. I have to admit I only gave it to her for a week, not two. She hated the taste and it was traumatizing for us both to give it to her, not to mention her sister Gus kept cleaning excess medicine off her face so vigorously that she was missing patches of fur around her face.
Recently, she's become very lethargic when in the cage. I took her to another vet, and they suspect that she is blind. They didn't check her ears again, but due to the fact that she has a severe head tilt and seems very off balance, I'm thinking that I really shouldn't have cut the medication short.
I'm just worried that this is a tumor, or something else that is not within my finances to treat. Do you have insight as to what this could be?

Answer

What makes you think she is blind?  

The only way to tell for sure is by the way the light changes the pupils.  

The proper way to treat inner ear infection is to take antibiotics at least 14 to 21 days and at least a week of steroid therapy as well.  She probably was not treated long enough.

Is she using her front paws to grasp food etc...?