Alan Jay Lerner and Frederick Loewe wrote the musical play My Fair Lady in 1956, which was filmed in 1964 by George Cukor. They claim to have based their production on a play written in 1913 by George Bernard Shaw, called Pygmalion. However, I am inclined to believe that this is a false base because the endings of Lerner and Loewe's My Fair Lady and Shaw's Pygmalion were exact opposites.
What could be more different than living happily ever after and spending a life in misery?--apparently not much, according to Lerner and Loewe. When they have Eliza Doolittle (played by Audrey Hepburn in the movie) come back to Henry Higgins (portrayed by Rex Harrison on the stage and screen), they condemn her to a life of misery and abuse. By returning to Higgins, Eliza's will be reduced to that of a second-class citizen. Higgins did not treat her with respect before she stood up to him at his mother's house after she had left him. He only admitted to respecting her after she stood up to him. He will never treat her well if she continues to crawl back to him no matter how horrible the things he does to her are. I believe that until Eliza learns to respect herself, she will not be respected by Higgins.
When she returns to Higgins, Eliza will spend the rest of her life playing the pet to his owner. He wants her merely as a dog to fetch his slippers, not as a human being to respect and care for. Eventually, Colonel Pickering (Wilfred Hyde-White) will leave and her only source of respect will have vacated the house. That will ultimately cause Eliza to lose what shred of self-respect she had left.
In conclusion, by adhering herself to Higgins, Eliza will be condemned to suffer a lifetime of unhappiness. Lerner and Loewe reduced her to this through their mishandling of Shaw's play Pygmalion. By not returning to Higgins, Eliza could resign herself to life as a working girl in a flower shop, which I believe she would have greatly enjoyed, as she does in the epilogue to the original play.