Have you never experienced this? She is obviously trying to move on, by making new memories. Saying "just move on" to someone who is obviously trying is terribly insensitive. I can't believe you would say that to another human being, honestly.

Her brand of "moving on" was to produce a similar event with the resolution to make it a positive one. It backfired. Instead of looking at the past, she needs to look at the future. Although this incident didn't necessarily itself contribute to the breakup, it is an example of what might've led to the breakup (as her now ex's comment may suggest). Even if it was her birthday, digging up the past isn't always the greatest idea. It isn't a callous observation; it's just a push in the right direction. The original comment was merely supposed to be quick, short, and to the point. In answer to your question - yes, I have. I can't think of a person who haven't in some way or form. Naturally, some are worse than others. Mine are probably somewhere in the middle. Certain emphases typically prevent me from taking less-than-peculiar action, but what I described above generally works well. Learning from the past is good. Dwelling on it, not so much. Right now, she appears to be doing the latter. She should be doing the former.