I don’t know enough from your letter to be able to answer your question. Yes, it’s possible your teacher was emotionally abusive and purposefully overstepped boundaries. But it’s also possible that she saw you as a kid who needed a lot of support and then unintentionally got overly involved.
Sometimes people who are trying to help don’t know how to draw effective but sympathetic boundaries. Since they are confused themselves, they give confusing signals to the person they are trying to help. As I said, I can’t tell from the information I have what went on with her.
Of more importance to me than figuring out what the teacher did or did not do is that you are feeling emotionally affected. It could be that the same vulnerabilities or needs that got you into this relationship still exist. I do think you need some help untangling your feelings and dealing with the low self-esteem.
I encourage you to get into some therapy to help you do that. You need some closure on the incident with the teacher. And you deserve the attention of a professional counselor who can maintain appropriate boundaries while helping you figure out how to go from here.
I wish you well.