If you did not do it, I’m not sure why you wouldn’t fight it - if the truth really is on your side.
You can check your Google Drive history to show your editing/drafting process.
I would not just let this “slide” as an “oh my fault, I was naive” as this will be a permanent record. Ask your counselor and also ask your teacher to see what you can do as YOU take this very seriously and it is a concern for YOU.
I once wrote a first draft essay regarding drones (a topic of my choosing) and how drone cinematography is also art. My teacher said it was too sophisticated and polished and was concerned I wasn’t using my own thinking. I spoke with her, about my thinking process, and explained that the words on the paper were 100% authentically and originally mine.