What does the juxtaposition of act 4 with 3 in Bernard Shaw's Pygmalion highlight about change?

In the Oxford dictionary, the definition of change takes on a few meanings. Among these, change is stated as meaning, 'To go from one phase to another' or 'To undergo transformation or transition'. At the end of act IV, the audience is aware of two changes in Eliza's character. Firstly, that she has had enough of being a 'lady' and will defy Higgins for his selfish motives, and secondly, that she can think for herself …

…because of the lack of recognition of her feelings and emotions. Towards the end of act IV, Eliza seems to have gained the ability to be able to have independent thoughts and actions. The juxtaposition of act III with IV highlights that Eliza does have the ability to change where she is and where she is headed; and that she doesn't have to put up with Higgins' criticism and patronization if she doesn't want to.