theoretical theological question

How do you forgive someone who refuses to admit that they did something wrong? If you are put in a position where you know someone did something despicable, but no one can prove it and they claim it didn't happen, how do you get closure? I tried reading "Forgiving the dead man walking" to get some perspective. She has some very valid points, but how about when the person who wrongs you is not viewed any differently by anyone else because no one else knows? What about when you have to see that person almost every day of your life? What about when other members of your family don't believe that person did anything wrong? What about when they say flat out that you are the one lying?
I don't know what the answers are, I can only guess that what I learn from the experience will someday help me reach out to someone else in a similar situation. I try to remember what Gary said in Sunday school. The things like this that happen are the times when you are "building your witness". Maybe some day I will write a book on the situation since I couldn't find one to help me figure it out. God has a plan that is bigger than me. God has a plan that is bigger than my family. God has a plan even for the person who wronged my family. ... I hate rationalizing,