like someone mentioned in a separate comment, you are conflating disease with disability here. when people become too old to walk without assistance, you wouldn't say that they have a walking disease.
Why not? We have some peculiar cultural memes related to accepting the inevitable end of life, which we perhaps should revisit. I see no reason to not consider aging itself as a slow-burn disease, one we'll hopefully cure at some point too.
This girl's disease was a genetic auditory neuropathy.
They cured her genetic auditory neuropathy.
Pedantic arguments about what it's called are missing the point. The person had a specific disease. It was cured.