What I'm reading here is that the other party is disappointed in discovering a small kink that neither of you know about until after the trade. She probably discovered it through feeling the spine and now that she knows it's there she sees it. If she planned to breed the snake she now has the dilemma of whether or not to breed a snake she knows is not perfect. Some key points here are:
1) You were not aware of any kinking and did not intentionally deceive her.
2) Since you drove to complete this deal, I'm assuming you met in person and she had the opportunity to inspect the animal for any defects before parting company and considering it a done deal.
It's probably no-win situation for either of you so try not to get too defensive or upset and I wish you both the best in working it out.
- Paul