Personally, if a reviewer has been disappointed in a book of mine for good literary reasons, I always try to say "you can't like everything" the next time I happen to see them, and maintain good relations. As for the sort of embittered hack who has never published anything, and can't understand why she's reviewing one's brilliant novel about Sheffield and not the other way round, the best course of action is carefully to get her name wrong in print and say, sorrowfully, "Sexually frustrated, poor her" the very next time one finds oneself on stage with a microphone.