What did Helen do to both her mother and Ms. Sullivan that was very naughty?

Helen locked her mother in the pantry, and she locked Miss Sullivan in her room.

One morning I locked my mother up in the pantry, where she was obliged to remain three hours, as the servants were in a detached part of the house. She kept pounding on the door, while I sat outside on the porch steps and laughed with glee as I felt the jar of the pounding. This most naughty prank of mine convinced my parents that I must be taught as soon as possible. After my teacher, Miss Sullivan, came to me, I sought an early opportunity to lock her in her room.