I think it's nice that she is thinking of others and showing social knowledge. However, I feel it is the teacher's job, not the child's, to ensure that everyone has a chance to be heard. I just cannot praise my child for keeping silent and hiding what she knows. I think many girls do this in middle school and high school, to their detriment. Of course, you don't want to be an obnoxious know-it-all, but in this case DD raised her hand for one out of 10 or more questions that she knew every answer to. BTW, when I asked who did answer them, she said one boy dominated the responses.
