Deafness is actually relatively common in Holland lops. It seems to be genetic. They can be that way at birth or it can develop as they age. So if she is deaf, it may not be EC related at all.
My Leopold is deaf. We were pretty sure before, but the vet did take a look at him and said she believed he was deaf too. How we tested it: Placed Wooly in the other room so Leopold was alone. Stood in the doorway to the bunny room with a bag of treats. Held treat bag up on the other side of the wall so it wasn’t visible to Leopold. Proceeded to crinkle the bag to see if there was a reaction. Leopold carried on, completely oblivious. Wooly, on the other hand, came flying down the hallway from the other room looking for those treats.
Leopold does not react to noises at all. There can be loud bangs or strange noises, he seems oblivious. The new neighbors had fireworks for the 4th of July. They were very loud and very illegal. Leopold was still oblivious even though it sounded like a bomb going off. You can sneak up on Leopold quite easily. If he has his back to you, you can get right up to him and grab him. He never knew you were there. In fact, I walked right up to him when he was engrossed in grooming once. I clapped my hands right over his head, he didn’t react. Finally, when he was finishing up, he happened to glance up and see me standing over him. Boy did he look startled then because he had had no clue I was there! Hopefully that helps some. 