When Helen was very young and struggled to communicate, she almost killed her baby sister by overturning her cradle. Helen had usually kept her doll in the cradle. One day, she discovered her infant sister sleeping in the cradle. Angrily, Helen turned it over. Her mother caught baby Mildred before she tumbled onto the floor. Helen was filled with jealousy toward her sister. She had been the youngest child until Mildred arrived. Helen hated how much of their mother's time the new baby took up, and she "regarded [her] little sister as an intruder" (The Story of My Life, Chapter II).
Later on in life, "Mildred and [Helen] grew into each other's hearts" (Chapter II). After Helen learned how to communicate, she developed a more positive view of Mildred. They spent time together and tried to communicate with each other. When Helen learned how to speak, "little Mildred seized [her] free hand and kissed it and danced" (Chapter XIII). Together, the sisters shared their joy.
Helen eventually attended the Cambridge School. Her sister began attending, too. While they were both at the school, Helen was very happy. She spent a great deal of time with Mildred. They regularly spent time studying together.
What started as a tumultuous relationship full of jealousy developed into love and admiration. Helen and Mildred became very close.