In Jane Eyre, Bronte makes liberal use of French in her dialogue. What does this say about her audience?
At the time of writing the learning of French (and other languages) was a prerequisite for any young lady of the middle class and up. Note how later on in the novel Jane Eyre begins to learn German from her cousins. Certainly, books in Victorian times were mainly read by the social classes that would learn French as a matter of course, and thus the use of French by Bronte in this novel indicates the kind of readership and audience that books reached in those days. For us today, if we have not studied French, this might seem strange and rather challenging or annoying, but I think we can safely assume that anyone who read this novel when it was published would have been able to understand the French easily - for it would have been expected that they themselves would have learnt this language.