Sometimes we can help her without a problem , but sometimes when we try to help her , she gets confused and frustrated because we may be teaching her something in a completely different way that they are learning, this makes us frustrated too.
My oldest is an honor roll student, as well, and gets very frustrated when she asks us a question and she doesn't understand what we are saying. I agree that a lot of times we are teaching her the way WE learned, and things are very different now. That confuses ME! She does not want to hear how "we" do (or did) things, either.
As for not asking the teacher, I would talk to the teacher. I'd also explain to your DD that if she does not ask the teacher when she needs help, her grades may end up suffering one day because of that. Also, get your teachers phone number and email address. Maybe when she has homework she can contact her from home so nobody will know. Good luck.