Not themes. I know, there are multiple meanings. But for my class (AP Lit) we need to state the meaning of the work in an essay and our teacher seems to think there is only one in every book.
Ray
The intention is ironic social commentary.
Unless you've misunderstood the brief, I can't imagine what planet your teacher is on. The idea that every book has a "meaning" is ridiculous, a throwback to a 19th century convention when novels generally had some kind of moral: virtue rewarded, wrongdoers getting their comeuppance, etc.
Pride and Prejudice, unless it's something trite like "Society is weighted against women, but if they play their cards right, they can do fine by marrying someone rich" or "Hoho, what complications arise when a couple well-matched in their egotism get the wrong idea of each other on first acquaintance", doesn't have any overtly simple moral or meaning.
If you have other examples of what your teacher thinks is the "meaning" of particular novels, you might be able to work out what's being asked for.