Eliza has learned to have a sense of self worth by the end of the play. She has succeeded at becoming a lady, despite her working-class origins.
This leads her to two realizations. First, she learns that by becoming a lady, she has unfitted herself for earning her own living. All a respectable lady can do is get married. Whereas before, it was perfectly reasonable for her to earn a living selling flowers, money-making would now destroy her new status. She chafes under this restraint, thinking it senseless.
Second, she realizes she can stand up to Henry Higgins. She no longer needs to put up with his arrogant commands and ceaseless verbal abuse. She does challenge him, showing she is fully human and demanding he acknowledge that, which surprises him greatly.
Eliza grows in self-esteem and assertiveness as a result of her experiences.
Obviously Eliza has learned how to be a lady by the end of the play--in spite of the boorish behavior of Henry Higgins. She understand all kinds of opportunities should be open to her, but she also knows she is now too well spoken for a humble flower shop, based on this class-conscious society. She also understands that speaking well, having money, and knowing the proper thing to say at the proper time do not mean a person has true class. Just look at her teacher! Finally, she understands she can't go back to being just a flower girl, and she won't.