What is the main character's disorder? Which capacity does it diminish? Which capacity does it enhance?

The main character's disorder is aphasia which prevents her from understanding the meanings of the words that others speak. Thus it reduces her ability to comprehend words. It enhances the capacity to hear the tones of words, with the meanings stripped away. Emily G. has the ability to her tones apart from meanings and can therefore focus more intently on the tone of speech.