Buyer Leaving Negative Feedback Call To Repentance

We just had a buyer leave negative and neutral feedback that we think unfair. She lied in her feedback regarding the colour of an item and in another positve feedback, she lied about the postage costs. The buyer did not contact us first, as Ebay suggests that buyers do, so there was no chance to discuss the situation, or to offer a refund, if she was not happy with her purchase. We then checked her feedback for other sellers, only to find out that she is doing this to alot of other sellers as well. In fact, this buyer finds fault with many of her transactions, so that even if she does leave positive feedback, her comments would still indicate that her ratings would be low ... We are not sure as to why this buyer is using Ebay to hurt people in this way. Perhaps she is just not happy, but then why keep shopping on Ebay? Wouldn't she be better off, just going to a store, where she could see the item before purchasing it, saving disappointment? Lying, however, is a different matter. As a Christian, I am obliged to forgive anyone who wrongs me and also to warn them, that if they do not repent of their lying, stealing etc., that they will find themselves in Hell for eternity.