Eliza comes very close to being a walking cliché. She's the poor girl from the streets who turns out to be a brilliant and beautiful young woman. She's smart, independent, and feisty. This sounds like a recipe for a cookie-cutter inspirational heroine, but, man, does Eliza have charm. For one thing, you can't hate a girl who howls every time she gets angry. And boy does she howl. We're talking "Ah-ah-ah-ow-ow-ow-oo!" (1.127). It should be said that a lot of the time Eliza functions as comic relief. Her howls, her indignation, her frequent exclamations of "Garn!" and "I'm a good girl, I am," and most notably her performance at Mrs. Higgins's party are all designed to make us laugh.
Throughout it all, however, we know that she's trying her hardest to achieve her goals. We feel for her when we realize that Higgins and Pickering are getting a little carried away with their experiments. By the time we get to Act 4, we're behind Eliza and, when Higgins ignores her, man, are we angry. By then she's gotten over all the things that made us laugh. She doesn't speak with a thick accent; her grammar is correct; she moves with poise and confidence. We here at Shmoop don't usually condone throwing slippers or shoes of any kind, but we understand when Eliza throws a pair at Higgins. Over the course of the play Eliza is transformed from a poor flower girl into a sophisticated young woman, but, perhaps more importantly, she stops being the butt of jokes and becomes a real three-dimensional character, someone for whom we can really feel.
Toward the end of the play we find out that she's not 100% confident – she starts again with the darn howling – and that she's not all sweetness and light. She shows Higgins that she's proud and she's shrewd, and tells him that she'd rather go into competition with him than be married off to some rich guy. Like Higgins says, she is his equal, but she doesn't want to go his way or live his life.
On a thematic level, Eliza serves to show us how messed up society is. Her transformation is a testament to the power of education and language. Her difficulties demonstrate how little "the system" appreciates her kind of intelligence. She's an inspiration and a warning, and she's anything but a cliché.