Mrs. Keller loves her daughter Helen deeply and feels great pity for her. As a result, she views Helen as not in need of discipline. She lets her grab food off everyone's plates during meals and she lets her rough manners go by without comment. Like everyone else in the Keller household, she feels Helen will never be able to improve her lot in life due to being blind and deaf.
However, Ms. Sullivan changes her perception of Helen. Mrs. Keller realizes her pity and permissiveness will only hurt Helen in the long run, and prevent her from reaching her full potential. So, she starts allowing Ms. Sullivan to discipline Helen.
Interestingly, the stage directions when Helen spells out a word to her mother for the first time, Mrs. Keller experiences a bittersweet reaction:
Kate comprehends it, their first act of verbal communication, and she can hardly utter the word aloud, in wonder, gratitude, and deprivation; it is a moment in which she simultaneously finds and loses a child.
So, in the end, Mrs. Keller becomes proud that her daughter will be able to have a more independent existence, but she is also losing a child from the nest, so to speak.