First, one must ask what the writer (Caroline) is saying, implying, or not saying to the addressee (Jane).

Second, we must deduce what the book's author (JA) is trying to say or imply to her readers (us).

These are two separate messages that may not be the same. For example, the information about the gentlemen being absent may have meant something completely different to Jane than it does to those of us who are reading. We will usually know more about the situation than the recipient of the letters does.