To forgive & To forget

I am blessed(cursed?) with perfect memories of events in my life.I could remember a lot.For example I could remember how an acquaintance was so bitchy 5 years ago .Last week, I did meet her again.I remember the event and the words she said 5 years ago.So I just stay away from her and I pretend that I do know her. We can't control the other person's action but we can control our own.I just refuse to be chummy with such woman. A friend likes to say I don't forgive and forget people easily.How to do that when I have clear picture of the event?