The payoff at the end leaves me a little dry because I have a hard time relating to the problem Hellen was facing. I would imagine it to only take a couple of minutes after the first spelling exercise to link a hand sign sequence to an object held in my direction.
Helen Keller had grown up, though, with no concept of "language" at all. Most of us learn the concept through early communication with parents and others, which teaches us to associate abstract words with their physical meanings, but after losing her sight and hearing at 19th months, Helen had nothing until Annie Sullivan came along. In the story she doesn't even really understand what she's supposed to be learning, until she has the breakthrough at the end - that's when she makes the connection. The triumph isn't that she's remembering words she's been taught, it's that she finally starts to understand the concept of language.
It is not actually that advanced of a language. Hellen only had to make a connection between an object and a symbolic gesture for it. Doesn't look like a large gap to bridge, but that's just me.