|It appears that you and your employee are neither literally nor figuratively on the same page when it comes to her writing. While you believe your editing is critical to her work, she apparently regards your editing as minimal at best.|
The first step is to look at her comments and see if there is even a hint of truth. Honestly ask yourself if the changes you are making are clearly improving the quality of her writing.
Assuming that your editing is essential, the next step is to review the way you are informing her of the changes that you make. You "briefly showed" her the new version, and that could be the problem. If you run the changes by her, she is not likely to either see or understand them.
You should actually use these meetings as an opportunity for coaching and training. Put the two documents side-by-side and discuss each change that you made. After all, your objective is not only to improve the report she has written, but also the reports she will be writing.