Yeah Working Girl is a good one. Ford's character isn't super-rich, but the choice between Weaver and Griffith (and her choice between Ford and Alec Baldwin) is definitely class-infused.
The rich heroines in The Notebook and Titanic are both good-hearted from the beginning iirc and don't need to change. It's more about their families' restrictions, though the "bad boy" attraction might be relevant. Danny and Sandy change for each other pretty drastically, though