How you deal with editorial queries is a matter of give and take. Obviously, the more personal your book, the more sensitive you are going to feel but remember that it is in the editor’s interests to make you look good by making the book as good as it can possibly be. If she says a section is boring (she may phrase it differently but you will know what she means), look at it again.
Is there anything you can take out? Can you add to it to make it more appealing? If you really want to dig your heels in, consider giving way on some other point that is less important to you. While you and your editor are busy getting the text right, the salespeople are starting to think about selling the book, and to that end they will prepare a jacket (for a hardback) or cover (for a paperback) many months in advance of publication.
Your contract will probably say that you will be consulted about jacket/cover design, but consulting means just that: the publisher has the final say and publishers vary enormously in their attitude to author input.
If you really want to dig your heels in, consider giving way on some other point that is less important to you.