To let her over the disappointment i think I would calm her down, with confidence will try to explain that what if she can't score good marks, she should try hard in the future !!!
and the second thing; blaming the teacher isn't good. The only solution is to attend the classes regularly and listen to the teacher .. and afterwards if she find the that she is not able to understand what the teacher is trying to tell then she should personally go to her and tell her the problem she is facing and how could she get over it ..
Please mark as a Brainliest