It's not a 'deaf gene' per se.

It has to do with the interaction of the white trait and the blue eyes
trait: a higher than normal percentage of blue eyed white cats are
deaf, but white cats with other eye colors are much less likely to be
deaf, and blue eyed cats with other body colors have only the normal
(rare) incidence of deafness from other causes.

The type of white also makes a difference: cats with the dominant
white gene are at risk; those that are merely 100% white spotted are
not.  The specific blue eye gene also plays an important role - only
those cats with a specific type of white coat and a specific type of
blue eyes will be deaf from that cause.

A Google search on

 "blue eyed white cats" deaf

will turn up quite a bit of information.

Why don't you just test your cat to see if she can hear a finger snap
behind her - one that cannot hear, as well as one that is ignoring
you, will not respond.  If the cat is used to responding to you
opening a can of tuna, you can open a very similar can (pineapple,
perhaps) and if the cat responds, it heard the opening - not
responding may mean only that the cat heard the difference between the
cans, though I don't expect that degree of discrimination in a young
cat.