Look.
Either she has gone to court and been granted guardianship over you, or she has not.
If she has done so by the time you turn 18, then you're stuck.
If she has not done so by the time you turn 18, then on your 18th birthday you walk out the door.
All your moaning about what she's trying to do is being wasted. She can threaten all she likes. She can even try to have you deemed incompetent if she likes. The ONLY thing that matters is whether she has succeeded or failed by your 18th birthday.
So instead of whining like a baby and proving her point, start getting your ducks in a row to leave. As Yoda said, there is no try. She either succeeds by your birthday, or she doesn't. If she doesn't, out you go.

