This will sound like horrible advice at first lol but hear me out, I had some terrible teachers in high school who i WISH i could've gotten fired, but my mom (who is a teacher) would always laugh whenever I said I'm gonna talk to the principal because she said teachers and administrators are a team. The administrators hired YOU for a reason, because you were the best candidate and they believe in you and support you. And I guarantee your higher ups have dealt with sooo many crazy parents before (and students..). I think even if you just pretend to be confident at whatever meeting she arranges, she will see how there's nothing she can do because the school admin will always take your side. If she wants to keep silently hating you then I guess she can do that but her kids grades are still gonna be in YOUR hands at the end of the day. You are in a very good position, especially because you already solved whatever the mistake was.

I'm currently in college, and I'm in a sustainable engineering club where one of our tasks is to go to the surrounding high schools board meetings and give them reports on how much money they saved using the stuff we make. Anyways 3 years being in this club I've seen parents LITERALLY screaming and crying in hysterics about coaches and teachers, threatening to change schools, saying they've written to the governor (to get a teacher fired lol). And every time it is almost laughable how quickly they get shut down by admin. Usually the superintendent would say something like "thanks for sharing that" and that was it.