[Pura Vida]

I'm sorry to read that you're going through this. It seems that the vendor should have done a better job explaining their expectations on the return, including the risk of the delicate finish on this particular model. The vendor agreed to ship two guitars for a trial period, so a reasonable amount of playing / use should be expected.

Offering an in-home trial implies a reasonable amount of risk, and it seems to me that you did not exceed it. I would refuse payment through my credit card company and consider returning the second guitar, as long as I was still within the return window and didn't have any more noticeable signs of wear.

Good luck -- I hope this works out for you.

Edit: agree with Mr. Paul. We're only hearing one side of the story, so it would be helpful to see the scratches.