I think Mutural retraction, still leaves the feedback she left, it just removes the netural icon. Not to sure, I'm sure someone eles can confirm this. I would not be nasty in the reply on feedback,(you do know you can reply on the fb you have already left) just give the facts and be professional, most buyers will understand, she was not patient, maybe she just used the delivery time as an excuse, because she did not like the product..just a guess.
And because I mostly sell used items, I will wait for feedback first, just in case. Everyone sees things different, and what one may see as good condition another one great, yet another one poor. If I were selling brand new items daily, then I think that leaving fb first is ok, but you never know, you are dealing with strangers. (funny while writing this, I'm watching People's court-and there is a lawsuit about Ebay-and leaving Neg FB).
Good luck! I feel for you!