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

Eliza's
returning the ring to Higgins is a sign that she's no longer prepared to be controlled by him.
Feeling used, not to mention fearful of what her uncertain future might bring, she has nothing
left but her few remaining shreds of dignity. Whatever Higgins may think, Eliza's a human being
in her own right, with all that that entails.

Giving Higgins back his ring
is one of the few ways left open to her of reestablishing some measure of control over a life
which for the duration of this "experiment" wasn't hers. Though Eliza's worried about
the very real prospect of returning to the gutter, at the very least she'll be her own woman
again, warts and all. But before that can happen, she wants to make sure that she has nothing in
her possession that...