I see no reason why she would be angry with you if that is what you are implying. If I were you, I would go to the banquet alone (if she is going and if you can go alone) and just fraternize with her, get a more formal date another time. Otherwise, skip the banquet as a gesture (if she won't go you won't go) and after a brief period, ask again for a formal date or such. Just hope the other crazy guy has no further internsions because that could complicate things. In my opinion. Perhaps she and you could keep your affair clandestine (secret).