She obviously did buy it in a rush but probably realised that it was a rushed decission. She might not be experienced ebayer and thought if she do not answer , the problem will go away .. this was not very nice from her.

On the other hand she offered you a compensation so you are not going to be on a loss .... unless it was an extremely good price ( for you) and you do not think anyone is going to buy it for this price. She was the only bidder ... Does it tell something ? ... I do not know .. just guessing . Why do you insist on selling it to her ?

I had myself few such cases . I generally do not make any fass about it . Ebay refunds selling fee if both sides agree that it was mistake  and I sell the item to someone else ..   Why make such a fuss about basically nothing .