Is it just on one assignment, or is this your average so far? If it’s your average so far, be prepared to have to answer the question of “Why haven’t you told me you’re having problems before?”
It doesn’t sound necessarily that it’s a “bad” teacher, it sounds like the teacher is harder and has different expectations than your other teachers. And perhaps that makes her a great teacher, but you just don’t realize it yet ( my clue to this is this statement in your question – you can’t study with her in the classroom) It sounds like she expects you to study on your own time, and that she lectures, and expects you to pay attention to the lecture.
That being said, you tell your mother that your teacher is much more like a college instructor and that you are having a hard time learning to adjust to her teaching style. Your grade is awful because you haven’t adjusted to more rigorous requirements, and that you are planning on meeting with the teacher to figure out what you need to do differently to be successful in the class.
And then you do just that. Don’t blame the teacher; her job isn’t to give you an A. Your job is to figure out what you need to do to be successful with different teaching styles. Sometimes that means learning to take notes differently, and putting in more time studying at home.