Well, from the way I see it, as bad as Catherine might have messed up, I don't think she was trying to reward herself. Not only that, I don't think she was trying to be completely dismissive of Nick's or anyone else's feelings. I think a) she wants the business to be taken care of first and then b) she'll discuss what she did and why she did it with Nick individually, if not all the CSIs, because he was the one who took it so personally. The guilt will definitely come out sooner or later, if not now. The characterization of Catherine is of a tough, hard-edged, no-nonsense woman. So maybe she does feel sorry, but she doesn't want to reveal all, and perhaps not in front of Keppler, who is still very new to the crime lab and still an enigma.