Her singing on the Guilty album does not seem to be affected by this. I don't know what limits she thinks that her right ear will create, unless her right ear is suffering too.
Constant exposure to sound - earphones, perhaps too regular visiting disco, whatever?? - seems to be what caused Ayumi's deafness. So, it seems likely to me that her other ear will affected too.
It is sad, though!
Talking about being deaf, it is known that Beethoven composed his best works being almost completely deaf in both ears.