You could title the essay "The Prisioner Doll" or "The Doll in the Porcelain Prison" considering that she was trapped among her bric a brac, kids, servant, and all the material possessions she so valued. But if you want to just go straight to the point another good idea would be to call it "Nora: A Victim of Circumstances" which is exactly what she is by literal standards.
My suggestion is: "Nora, No More" representative of her newfound independence. It encompasses the fact that she is not the same person she used to be. OR "The Rebirth of Nora" for obvious reasons. When you're trying to come up with a title, think about including some aspect of the character's personality or a word descriptive of what the play is about. Good luck! Hope you like my suggestion as I'm a free-lance writer/playwright. If you need any typing done or papers edited, I work cheap and fast....just let me know. I have two college degrees and majored in English and Theatre.