Let’s break this down:
I have this really hard teacher and everyone fails her class. If everyone fails her class, then it would be a big, red flag to the school administration, even if she has tenure. They would be on top of it as, a.) most schools like to see high GPAs for their students, and b.) parents complain; complaints require follow-up.
I failed her quiz, as well as 9 other kids. Unless there are only 9 students in the class and she only teaches your class and not others, that doesn’t equate to ‘everyone’.
Then I got a C+ and my mom is thinking of calling the school, teacher, principal, and NO ONE does that!! I cannot speak for what happens at your school, but I can speak for the ones where both of my sisters teach. Trust me…they are both known for being tough and have had more than their fair share of parent/teacher conferences, as well as a few confrontational meetings with upset parents. They both appreciate the care that the parents give in being concerned about the performance of their child. It is much better than not hearing from those who have a child that is floundering.
I’ll seem like a nub, and plus what will she say? Excuse my ignorance; I have no idea what a ‘nub’ is, but it sounds like something classmates would use in a derogatory manner. As long as your mother keeps this between you, the teacher and herself, there is nothing to worry about. There is no telling what she will say, but your insight into the current situation from an objective perspective will only help in having her keep her temper.
I already have a tutor Has your tutor talked to the teacher? Surely, that might help.
And here is the good news. If the teacher is really good and just making you stretch instead of coast, you will appreciate it in the long run. I’ve heard from several of my sister’s former students who felt the same way that you do right now. They have all said that while their grades were disappointing at the time, it truly helped prepare them for college life. One class and one final grade hasn’t stopped any of them from getting into the college of their choice, at least from what I’ve heard.
One other thing to keep in mind: there are very few people who excel or exceed in every subject. My cousin who is exceptionally book-smart and received his PhD from MIT has his own short-comings as a human being.
As @CyanoticWasp said, your mother is already proud of you. If she were not, she wouldn’t be so concerned about this one course and this one teacher. She sees how much potential that you have and wants the best for you. If you can look at it from this perspective, it may help. If you talk to your mother about how you are feeling and your concerns about her reaction, it can make the world of difference.