Sometimes I think people come from such different places that it's all words and no communication. I recently had a conversation of this kind with my sister in law. She told me, among other things, that her son needs preschool because, unlike my DD, he has never been forced to sit still and listen to people read books. Aack!!! I was horrified. I would never make DD sit still and listen to a book. I rarely even volunteer to read books--she just asks me. But I kept my mouth shut and a few days later I realized that she was just trying to make me feel better about DD not being in preschool. So, even though her facts were way off, and her parenting philosophy is hugely different from mine, I can appreciate that she was trying to be supportive.
You might find, if you reevaluate this conversation with your SIL, that she was actually trying to praise you for educating your DD. Maybe when she said that young kids who read do so by memory she was trying to acknowledge your DD's advanced memory. Maybe she was trying to reassure you that your DD isn't as advanced as she seems--and, while that might seem negative, she may have meant that in a good way. And maybe, even if she really was being as snarky as it sounds, you could try to take it in a positive light for your and your DD's sake--or just to spite her.
I also want to say, very gently, that sometimes our worries about others' reactions become self-fulfilling prophesies. I know that you felt pressured to hide your DD's abilities, and it sounds like you didn't do that, but there was probably a good deal of defensiveness on your part that colored your perceptions as well as your reactions. Sometimes the best defense against this sort of thing is no defense at all--just blind, determined cheerfulness.
