Quote four sentences which prove that Miss Keller has made full use of her sense of touch in The Miracle Worker.
The tone of your question suggests that you would like to hear about how Helen has made full use of her sense of touch even BEFORE the appearance of Annie. In my opinion, the episode about the doll is the best example:
(Helen meanwhile sits on the floor to explore the doll with her fingers, and her hand pauses over the face: this is no face, a blank area of towel, and it troubles her. Her hand searches for features, and taps questioningly for eyes, but no one notices. She then yanks at her aunt's dress, adn taps again vigorously for eyes.)
Aunt Ev: What, child?
(Obviously not hearing, Helen commences to go around, from person to person, tapping for eyes, but no one attends or understands.)
Please note that the most pertinent four sentences here are sentences of stage direction, not dialogue. People who can see/hear, of course haven't refined their sense of touch. Helen has already lived years without those two senses so, even though she is rough around the edges, she certainly does make full use of that sense.
Interesting that the description begins with the explanation of Helen wanting "to explore the doll with her fingers," something quite common for her, I imagine. (Perfect evidence for your argument.) Of course, Helen uses her sense of touch further to determine (first other features) and then that the doll doesn't have eyes.
It's also interesting that after being used for exploration, touch is then used to grab attention. First, she gently taps the doll using her own touch in hopes that someone will notice. Next, she "yanks" her aunt's skirt. Third, her taps for eyes become "vigorous." Fourth, she approaches everyone else in the room, still tapping for eyes.
Poor Helen! Enter Annie, ... and Helen's world changes. : )