(She drops her eyes to spell into HELEN’S hand, again indicating the card; HELEN spells back, and ANNIE is amused.) KATE [TOO QUICKLY]: What did she spell?

ANNIE: I spelled card. She spelled cake!

(She takes in KATE’S quickness and shakes her head, gently.)

No, it’s only a finger game to her, Mrs. Keller. What she has to learn first is that things have names.

KATE: And when will she learn?

ANNIE: Maybe after a million and one words.

(They hold each other’s gaze; KATE then speaks quietly.)

KATE: I should like to learn those letters, Miss Annie.

What does the dialogue reveal about Kate?
She is strict with Helen’s discipline.
She is hopeful that Helen can be taught.
She is unwilling to assist with Helen’s learning.
She is proud of Helen’s ability to spell correctly.

She is hopeful that Helen can be taught.

Explanation:

We can see that Kate is invested in Helen's learning. She wants to know how she is progressing and when she's expected to make more progress. Now, she is expressing the wish to help her learn more - she wants to learn letters that Miss Annie is teaching her and teach her as well. She is hopeful that Helen can be taught and wants to increase her chances.

taking into account that a theme is the central topic a text treats and can be developed through a story, play, poem etc. the following are themes that can be further developed:  

my best friend jeffrey has many unusual interests. (the story could be about each of the unususal interests)

once a man gives his soul over to evil, he can never go back. (this could be a saying or a proverb)

the three sheepdogs lay around the yard all day. (it could be developed detailing how each of these sheepdogs lay around)

a priest's collar has an unusual effect upon people. (it could be developed detailing the different effect upon people)

innocence is a powerful force in a world full of corruption. (it could be developed detailing how is a world full of corruption)

king lear is a play shakespeare wrote later. (it is just a sentence and doesnt give any idea or topic to be discussed in details.

evil often wears the disguise of innocence. (this could be a saying or a proverb)