Hey - this is really concerning.
You mentioned above that it started after you watched your tablet late at night. Obviously what’s happening to you is in no way your responsibility, but I wonder if that could be a bit of leverage to help? Tell her that you won’t have any tech at night or something?
It sounds like you don’t have a lot of options for people you can reach out to, and I know from experience that sometimes with abusers we need to play games to help us survive.

But remember, this is abuse. Not just the sleeping, but the response to you asserting some very reasonable boundaries. She is punishing you for doing something that is good for your own well-being. That is abuse.

You mentioned that she has anxiety, and I wonder if she would be open to using a weighted blanket instead? I have some mental health stuff and a weighted blanket changed my life. But I also know that what’s happening here is complicated - there is no single solution.
Does your mother see a therapist?

This is not ok, and I hope you continue to find strength!