What happens to Miss Sullivan's character during The Story of My Life by Helen Keller?

The Story of My Life is Helen Keller's autobiography.  She wrote the book to record the events of her life up until she was in her early twenties and in college.  Annie Sullivan arrived in Alabama to be Helen's teacher and companion when Helen was six-years-old.  This time period means that only about fifteen years of Annie Sullivan's life are covered in the book, which I detail below.

Anne Mansfield Sullivan was sent to Alabama from the Perkins Institution for the Blind in Boston.  Helen described the day that Annie Sullivan arrived as "the most important day [she could] remember in all [her] life."  Ms. Sullivan was determined to teach and train Helen.  She found this challenge to be more than she had expected because of Helen's extreme stubbornness.  After many attempts to teach Helen the manual alphabet by fingerspelling into her palm, they had a breakthrough moment.  One day, Annie Sullivan led Helen to a water pump and let the water flow over her student's hand while spelling the word into her palm.  Helen described that moment in her autobiography, saying that she "knew then that 'w-a-t-e-r' meant the wonderful cool something that was flowing over [her] hand."  From this time on, Helen became an eager learner.  Miss Sullivan was Helen's teacher and her companion.  She accompanied Helen as she travelled, met famous people, and attended school.  Annie Sullivan supported Helen and continued to communicate with her using the manual alphabet while Helen went to high school and college.