I'm sorry to hear your buyer want to return the pony - thats always disappointing .
I agree with Ponylady though - you handled it well and are making the effort to keep your buyer happy by giving her more than one option
Like Ponylady said, you dont need to refund her return postage. The buyer normally pays for that, and ebay doesnt require that the seller pays it (you only normally refund the cost of the item and the original postage), but if you find that it was your mistake rather than her buyer remorse, then it would be a kindness to offer to pay the return postage as well, though you dont have to
Please let us know how it goes. Hopefully you and your buyer can work this out soon