First, so proud that you have reached out to this forum, your posts are being read by other terns
in your situation, who for whatever reasons are not able to post.
I know exactly what you are dealing with. My neice had the same situation with her mom. No one in her family believed her and her sister, (living in Israel at the time, ). She finally came to live with me which did cause problems in our family, and is now an educated, happy, engaged, young woman.
It was not sn easy path for us, but she was stubborn and strong and insistant. She went thrum therapy and surrounded herself with people who were positive influences.
I hope you can find an adult who can be supportive.