You are not wrong, but not right either, her hair is basically brown but with an slight purplish tone (but still brown), so its not weird to find lot of fanart of there with her with purple hair. Anyway you can adjust it to your liking, just by prompting "purple hair" or "dark purple hair". Same with the eyes they are meant to be brown but they were a redish brown not pure brown, so you can go with "red eyes" too