What did Ms Sullivan mean when she claimed that Helen had language if she was referring to someone who was deaf, mute, and blind?
Language is the ability to communicate. Helen can communicate her feelings, but only in an undisciplined manner, such as throwing a fit. What Helen doesn't have is the ability to express the meaning of language, and this is why Annie wants to teach her hand symbols. Annie tells Kate, Helen's mother, that "Language is to the mind more than light is to the eye." The need for humans to be able to express their thoughts and feelings throught communication is essential. This is one reason why the last scene is so powerful--Helen finally learns the connection between language and meaning when she realizes what water is.
One must remember that language does not mean an oral language. Language is the ability to communicate. It could be a written language, such as Egyptian glyphs, it could be American Sign Language (a visual language), or it could be a language like we are aware of most often like English or Spanish. Even if Helen is deaf, mute, and blind if she is signing and communicating through signing, she has language.