Personally, I would say something. Otherwise your daughter is going to be forced to write in error going forward.
Ask for a minute, go in armed with your Bedford reader or something similar and show her where she is in err. Don't make a huge deal out of it but let her know that your DD worked really hard and was upset by the grade. Tell her what you do for a living. The teacher will either apologize and change the grade or not. Going forward your DD needs to continue to make the same "mistake" so that she doesn't inadvertantly relearn it wrong. I'm willing to bet that even if the teacher doesn't change her grade, she won't make the same mistake again.
