Okay. Let's be fair. Rather than saying she missed the main point, I should say I did not convey it effectively. Either I was ambiguous or I did not highlight it properly. For a trait or pivotal fact about the character, this is easy to fix. Here are some approaches:
- Looking for potential misreadings - Heinlein said the best class in writing he had was one on giving orders. He was at the U.S. Naval Academy, and, after providing a situation, the student of the day had to write and order. If it was completely unambiguous, he got and A for the day. If anyone in the class could find a way to misinterpret it, an F. Reread the key sentences with no mercy.
- Repetition - If it's important, keep mentioning it, and it will stick. (This is painful for me to do.)
- Providing a metaphor - If, for instance, I say that a character is a giant, you'll probably remember he or she is big for the rest of the book. Using an unusual word, like gargantuan, can work, too.
- Making it consequential - If I tell you a character was abused as a child and then show him or her shirking away from a friendly touch, it's likely to stick in your mind.
A classically difficult way to deliver and emphasize important information is through dialogue. Often, the words are too obviously coming from the writer, put into some poor character's mouth. Even worse is every exchange of dialogue is an opportunity to build characters and make them come to life. Having them dump essential information and speak unnaturally degrades them and kills that opportunity.
One more point: Different readers often attend to different things. A reader of Regency Romances may see a character revealing himself to be a cad based on how he presents his card -- something other readers would miss. A reader of SF could be relied upon to understand an encounter with a minor, but unexpected, source of gravity by a spacecraft on a long mission could be fatal. Those who love Thrillers may be primed to note the failure to encrypt a text message.
But it is best not to assume your audience will detect subtle points. Test with readers to be sure. And don't do what many writers do. Don't tip off your early readers by providing a logline or summary that makes all the essential points. If you do, they may not notice that you did not do the job where it matters, in your story.