I'll read these responses too because I have a tendency to be like your wife and my boyfriend is always telling me that we can't move forward if we are always living in the past. Which is true. For me, I think the issue is I feel that if I don't watch carefully and keep track I will end up getting hurt -- hey, the past repeats itself, right? I have no way to know if this is also true for her, but it may be an insecurity on her part. That doesn't excuse it, but it might help to explain it. My bf is also the same in that he has stuff about me that bugs him, but he doesn't tell me. And I want to know because I figure that I can use it to grow. I also think that letting things build up is bad.
Have you talked to her about it? Asked her why she does it? I think you could definitely try the Non-Violent Communication techniques here with good results.