I agree that this situation seems extreme and it does sound as though the mother may be going too far. Though I do believe students should always have someone edit their papers. Ideally the editing process is also a learning process. I will always encourage my children to have someone edit their papers. I would have never turned in a paper without having someone edit it. Professional authors have people who do this. They are called editors.
I suspect behaviors such as what this mother displays is why this recent generation of parents is called "helicopter parents."