Scoops!
I think your response looked good. But do not let it put you off from selling on ebay. It can happen anywhere, it's just the luck of the draw in some cases. I have met some wonderful people over the years through ebay and I wouldn't change that for the world.
I think you handled it tackful and professionally. I don't think there was much else you could have done to prevent a neutral from her. She seemed to not completely understand what was going on from the get go.
I am just glad it is over with for you and you can move on and not have to deal with it.