Was Helen Keller the first blind deaf person to learn how to speak with her mouth?

No, she was not.

When she was little, and when she was about ten years old, she found out about another blind/deaf little girl in Norway, I think that her name is Ragnhild Kaata.

When Helen Keller learned of Ragnhild Kaata, she was determined to learn how to speak with her mouth as well.