What does Kate realize about her relationship with Helen at the end of the story?

Kate realizes that it is Annie (Teacher) who has become the primary influence on Helen’s life, even though she is her mother. It is Annie who has found the secret of communicating with Helen, which Helen recognizes at the water pump. In order to communicate with Helen, Kate must learn from Annie the finger alphabet and how to reach Helen. It is true that Helen learned some self-invented sign language to communicate with her mother, but she did not learn anything beyond the basic requests of childhood. To go on to advanced and abstract language, all teaching must come from Annie, both for Helen and for Kate. Kate has taken a step back as a mother, allowing Annie to be the primary source of knowledge and even love and affection. The family has become secondary; the teacher has become primary.