TAKE THE MONEY AND RUN!
I would not even consider keeping her. For all you know she could have internal health issues that you are not aware of. And I would say that at the very least you need to be concerned about the possible intestinal impaction caused by that kink impacting her ability to pass waste properly. And as stated before you should demand that they not only pay for the return shipping (including the heat pack, packing tape, etc ) but for the original shipping. They hatched her, raised her, sold her and shipped her and they are trying to tell you that they never noticed the major kink in her spine. Then on top of that they are trying to tell you that the deformity won’t cause any problem with breeding and that it is for sure not genetic. And they know all this from the picture you sent them because this is of course the first they’ve heard of this kink, hhmmmm. If I were you I’d be pissed. In fact I am pissed and this incident really had nothing to do with me.