I think it's a pretty sharp looking gecko that you have shown interest in prior to all this mess. It may feel to you that "justice" isn't being done because she doesn't get "hurt" by the solution (ie: actually give up some of that money you paid)....but is that really the most important point here?
You can stand on principle and demand a refund of cash or nothing at all....and you can end up with nothing at all. OR...you can get a really nice gecko in addition to the one you already have. Is the pair of them worth $450? I don't know....but the pair of them is worth a heck of a lot more than the plain one by itself.
Obviously it's up to you. We can talk all day about what we believe would be the "fair" or "just" solution...but in the end, such talk is powerless because she is set on her course. If I were in your shoes, I'd accept it and move on. The "hurt" you wish her to feel in losing the money you gave her will come in lost customers.