When she says "there are plenty of times when I didn't do it", she is invalidating you, and she is dismissing and deflecting the issue you've brought to her attention. Instead, the healthy caring response would be, "Oh I'm really sorry that bothered or hurt you. I will be mindful of your feelings and will not do that again". And when she says "you brought this up a while back", again she is not validating you and treats it as though it's a nuisance to her because it's been brought up before. Yes, these are tactics used to confuse and avoid any real discussion or resolution. With abusers, there is never any resolution to the issues you bring to their attention because they refuse to talk about it, to validate you, or to resolve it in a healthy manner.