I once had a deaf Dalmatian. We were advised not to keep her as we had young kids at the time, and the trainers/breeder felt that if the dog ran out into the road, the kids would follow to try to stop her.... We gave Mollie up and welcomed home Phoebe her sister instead. Many animals with white coats can run to deafness. How we confirmed the deafness was to wait until she was asleep in her crate, and then make a loud banging noise with two metal bowls and watched....there was no reaction, so that confirmed it to us, and sadly we let her go. She was rehomed with someone who was more able to cope with her abilities.
It is possible to train a deaf dog via hand signals. It wasn't for us at the time, but others have had great success with it. My daughter has a deaf, three legged cat, again, white....she lost a leg because as a kitten she ran out into the road, and was hit by a car.
our Vizsla could hear a pin drop, when you think she is comatose asleep, the rustle of her cookie jar in the kitchen, or the freezer door opening, brings her running. They are good at ignoring you when it suits them, (not wanting to go out in the rain to toilet for example), but in general this is a dog that just wants to make you happy, they rely so much on us praising and loving them. It sounds to me, no expert, like she has an issue. I hope you get better answers than mine from other more experienced vizsla pawrents, and that you find a solution that works for you. Maybe she just has an infection, that is affecting her ability to hear.