In Pygmalion, what is the symbolic significance of Eliza returning the ring to Higgins?

I would want to argue that this important scene at the end
of Act IV is linked in to the wider and more far-reaching trasformations that have
occurred in Eliza. Higgins is of course only focused on and aware of the external
transformation, which is the source of his bet. Having succeeded in transforming a
flower lady to a duchess, he is blind to the other transformations that have transpired
within Eliza. Eliza here clearly shows the independent spirit that she now has. Her
returning the ring that was bought for her by Higgins in Brighton symbolises the way
that she refuses to be objectified and treated like a project by Higgins anymore, and
demands to be able to relate to him like another human being that is his equal. Note
what she says and the way that the stage directions indicate that Higgins responds to
this challenge:

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This ring isn't the jeweler's; it's the one you
bought me in Brighton. I don't want it now. [Higgins dashes the ring violently into the
fireplace, and turns on her so threateningly that she crouches over the piano with her
hands over her face, and exclaims] Don't you hit
me.

It is clear from his
response that Higgins is aware of the symbolic meaning of her action. She is challenging
the way that he thinks of her and the way that he is treated her, and trying to get him
to see, as he is forced to concede in the next Act, that dignity and self-worth are not
a matter of outward trappings, but of how you treat others.