for both of you. Its horrible the way that school stresses children out these days isn't it.
I'm not sure that I can offer any constructive suggestions but maybe you could sit down with your DD to have a talk about school and maybe explain that while it important to try and do well at school that its not the be all and end all - that there are other things in life that are also important and that even if she gets the odd C that she's a wonderful person which is more important.
Does she participate in any sports teams or so on? Maybe school won't stress her out so much if she has other extra-curricula activities to focus on.