I had a terrible experience with my last vocal teacher. She really put me down and i don’t want that experience again.
Get a teacher who won’t put you down. Teachers are there to teach you how to accomplish your goals. It sounds like she had some serious insecurities but all teachers are not like that.
Sometimes you just have to get back up on the horse that threw you. Interview teachers before you sign on with them, talk to their other students, and then choose a teacher that will help you.
But honestly, to improve a voice it’s best to seek professional help. Otherwise you could end up doing something to your voice to ruin it altogether.