Start with the teacher. Make an appointment or go to her help hours and say that you would like more specific feedback on the essay. In fact you would like to keep revising this essay until you can get at least a B. I did this one time with a teacher…I really wanted to learn what she wanted.
Ask her if there are any books that could help you. One that talks about sentence structure and things like using transitions between thoughts, etc.
Ask for examples of what a D vs B essay looks like.
If she will work with you, then great! Keep at ,this. In the future, bring in drafts early and work with her on that.
If she wont’ do anything helpful, then go to the head of the English Department. Tell them that you are wanting to learn what is expected at ABC HS, and that you didn’t get actionable feedback so you went to office hours and she would not work with you. Can they suggest a path forward?
Also get a tutor to help you…Your National Honor Society will probably have some.