You’re right. Your mom is completely unreasonable. My only guess is that since she lost her mom when she was your age, she has no idea how to be a mother to a young girl. It also sounds like maybe she is scared of what’s going to happen now that you are approaching your teens. Many parents don’t know how to handle it when their daughter starts to look and act more like a young adult woman. They try to “protect” their daughter by making her look ugly and limiting where she can do and what she can do. It doesn’t work, of course. It only makes the daughter resent the parent.
The yelling and fighting have to stop. You have six more years before you will be old enough to leave home and take care of yourself. You’ve tried to talk with her and it isn’t working. I think you need to reach for some help from another adult. You didn’t mention if your dad is in the picture. If so, that may be the place to start. If not, think about another adult you trust who would be able to help you and your mom talk about how to have a better relationship through your teen years. That might be a trusted teacher, a school counselor, even your doctor. You need someone who isn’t going to just blame and shame your mom but who can offer your mom some support and help. (It doesn’t sound like your grandpa is the right person since she says he’s been mean to her.) You can’t do this alone.
If you want someone to talk to as you work on this, I suggest you call the Boys and Girls Town Hotline. There are counselors available 24/7 to talk to kids like you who are having troubles and don’t know where to turn. The calls are confidential and free. The phone number is 800-448-3000. Please give them a call. They may have other suggestions for you. They can certainly give you some support.
I wish you well.