In Pygmalion, Eliza believes that she owes everything she learned about being a lady to Colonel Pickering.
In Act V, Mr. Doolittle, Eliza's father, has come to take her home. Mr. Doolittle is now a very wealthy man on account of Ezra Wannafeller, who has bequeathed him the sum of three thousand pounds a year, in 'exchange for lecturing at his Wannafeller Moral Reform World League as often as they ask,' for up to six times a year. Mrs. Higgins is genuinely happy for Eliza, as she reasons that the poor girl will now be provided for. Higgins, however, isn't too happy about this new development. He wants Eliza to return to him, as he believes that since he created her out of 'the squashed cabbage leaves of Covent Garden,' she should readily do whatever he says.
However, when Eliza comes downstairs to meet with Pickering and Higgins, she admits to Pickering that it was he who taught her how to control her temper. She thanks Pickering for teaching her the proper way ladies and gentlemen ought to behave. In one of the most famous lines in the play, she asserts that a woman becomes a lady when she is treated like one.
...the difference between a lady and a flower girl is not how she behaves, but how shes treated. I shall always be a flower girl to Professor Higgins, because he always treats me as a flower girl, and always will; but I know I can be a lady to you, because you always treat me as a lady, and always will.
Eliza reiterates her admiration of Pickering when she later tells Higgins that Pickering 'treats a flower girl as if she were a duchess.'