It's difficult to explain 'why', since we're talking about a (self-styled) 'god'.
However, I can say this, straight from the heart: any being, no matter how technologically advanced, that sets itself up as a 'god' over humanity, isn't worthy of our attention, much less 'worship', since it appears to be pre-supposed that, by our very nature and lack of technological advances, we don't know any better.
Perhaps you might ask your mother to consider this: the JW's were created by a mere mortal - a man - for his own reasons and purposes.
Perhaps researching the history of the cult's beginnings, might help her ask more relevant questions?