Hi Sweetpea, welcome to TP
I'd say that being deaf and having AZ is pretty common and sadly a lot of people with AZ lose their hearings aids and never get them replaced, my wife for example.
I would have thought having been deaf virtually all her life your mother has the advantage of being used to living that way as opposed to someone who becomes deaf later in life.
Effectively about half the people in care with my wife are deaf as they have impaired hearing no longer wear hearing aids.
I'm sure over time both your mother and you have developed a coping strategy for her deafness in a way that the rest of us hasn't so al we can do is learn to shout louder.
K