It's going to hurt! It would be a like a surgeon saying I'm going to operate on you but it wont't hurt. It is going to be painful not just for her, but for you too. If you care anything at all about her, and it sounds like you do because you don't want to see her hurt, then do your self justice by being honest, not brutal, but kind and understanding of her pain. You do that , and your a stand up guy in my book.
best wishes.