In short, no. You will always be the author of your own work. An editor's job isn't to change that, or to make you alter something against your wishes. An editor is there to make suggestions, to give advice and to point out inconsistencies.
You may find that you agree with 90% of what an editor says – or maybe only 20%, in which case ask yourself if this is the right editor for you!
Editors will often frame suggestions as queries, asking you if a phrase or passage might work better in a different way. Sometimes editors will mark suggestions directly into the text (but in a way that you can undo them if you don't like them).
A client once asked me if I would be offended if she didn't take on board a couple of my suggestions. No! Not at all. This is the job of an editor. We read, we use our expertise, we act as critical friend, reader and adviser. We are professionals who know that you are the author and we are there to help and support you.
Editing is a very subjective art. You could give 50 editors the same manuscript to work on and get back 50 very different edits. None of these would be wrong, just different ways of approaching a text and a story. This is why it is so important to do your research in advance and find the editor who is the best fit for you and your book.
If, however, you find you are struggling to accept any changes to your manuscript, you may find that you are not ready for an edit. Writing a book is tough; editing can sometimes be tougher. Asking a stranger to read, critique and suggest changes to the manuscript that you have toiled over for months – maybe years – is hard.
It isn't unlikely in a developmental edit that an editor might suggest cutting a character of little importance in order to tighten the cast, or to remove an entire scene which has no bearing on the unfolding story and simply slows down the pace. But that character and that scene represent your hard work, your ideas, your inspiration. We understand – it's a hard process.
But when you find the right editor, you will grow to trust their decisions and advice. The right editor will have the best of intentions for you and your story.
So, no. You absolutely do not need to accept all the changes an editor suggests. But if you find yourself the right editor, you can be confident in accepting most of them.