The best thing to do is to try and get her to point out the times when you tend to be sarcastic (at the moment of its occurrence) If she is having hard time giving you examples this may be most helpful to both of you.
It may be possible that she is misreading some of your statements. Men are usually more direct and up to the point when conversing while women tend to interject more of emotionality when describing something. There had always been differences in how men and women relate and process information.
You cannot try to correct something in your behavior if you do not know what exactly that thing is. If willing, have her perhaps use a small tape recorder and then play back some of the examples for you.
Have her give you examples in her own language of how she thinks something should have been verbalized.
Thank you for clarification. The problem of miscommunication appears in all relationships. There can be character differences (like you've specified that she is more general about things while you are more detailed) What would be of importance is to find out why this is bothersome to her. It is possible that she is upset about something else and instead of talking about that, is focusing on something else less significant.
Try to think about when her criticism started (unless it had been something evident from the start of the relationship) The issue may be that she is frustrated with herself but then is projecting her own shortcomings onto you as a way of self defense.