This is correct. The buyer had a chance to put eyes and hands on the animal before putting down any cash - if she has misgivings about the snake's condition she should have walked away then. It's very different when you pay for an animal that gets shipped to you and it was misrepresented.
I'm not surprised breeders don't give a guarantee past live arrival. On this site we've seen inexperienced keepers end up with sick or dead animals through ignorance or bad advice. Unregulated heat, too much or too little heat, improper use of insecticides or chemicals in the enclosure, unmonitored live feedings, lack of proper quarantine, etc. - the seller has no control so why should there be a guarantee?