My mom is going to cut all my hair off while I sleep because she doesn't like me straightening it. My hair isn't damaged, but she got anger-issue-level mad at me and screamed this at me. I can't lock my door. How do I hide? 

 She is serious 😢

If she has done similar things before I would talk to your school councilor about it, or to another responsible adult. They can help you get out of the situation.

If this is the first time she has acted like this, I would assume that something happened earlier that day/week/month that is stressing her out. You should ask her if everything's ok or if there is anything you can help her with.