I'm going to ring in a sympathy vote for your DD! It's pretty hard to balance giftedness with compassion, even for grown-ups. Gifted kids/adults tend to tell the truth as they see it, in hopes of solving a problem...whereas the more "group-aware" person may hide the truth to ease feelings.
And yet we tell out gifted kids that their giftedness is wonderful, and they shouldn't hide their light under a bushel!
Man! It takes being gifted to DEAL with being gifted!
Having said this, I don't mean to steal your thread. I would tell my DD that we always have to find the "middle way" when dealing with the equally worthy goals of displaying our giftedness vs. taking everyone's feelings into consideration. Each situation is different. I would reassure your daughter that she's still young and she's still learning, and that she can find a way to correct people without making them feel bad. No doubt she WILL be in a leadership position one day, with responsibilities over others, and will need to learn about management. I bet she would love a book about people skills, managing others etc. and would eat it up!