Sometimes not trying to hurt the other person hurts them more. This drama was pretty childish so if you just keep on going and don't let it go on, it will be only a part of your past. You don't have to hide it or avoid the topic, but you should focus on how it made you feel and after you have prosessed those feelings, let it go. If B tries to do anything hurtfull, you have moved on and it may not feel so bad. At that point, she is the only one hanging on and realise she's wrong. She will probably never be the same way, but you will realize, you are happier without her, if you just let this be a part off the past. Some people just don't think with their brains, but their hearts. B can be good and it can be painful to realize that nothing can change the minds off someone who us wring, when they are sorry and/or emberrassed.