The editing process can sometimes be quite demanding for both editor and writer. The author has made the text as good as they can – perhaps having edited it several times already, and she may have also used a critique group and beta readers. Now we’re asking her to make even more changes.
The editor usually sees things the author has not noticed. Even so, there is still the possibility that she may be stuck in a rut or cramped by a house style that has become formulaic.
It’s good when the editor and author truly work together. The editor establishes what still isn’t working – going from the more global down to the line edit. The author finds a way to respond and maybe continues to look for improvements beyond what the editor has suggested. This seems perfectly acceptable. The writer has been away from their script for quite some time probably. They can now be more objective and chances are they have also improved as a writer; if they’ve continued to write they have no doubt also continued to grow as a writer.
We always need to remember that we’re on the same side. We both want the book to be as good as it can be. It doesn’t matter at all that the author subsequently spots something that the editor had not. Then of course it’s part of the editor’s job to notice what the author has not.
Team work after all. It always works best if both parties see it that way.