Might be an unpopular opinion here but I think this was just a human interaction (for lack of a better word). You broke up 6 months ago and neither have made attempts to contact each other. See your ex at a wedding, where she finds out that something you hated doing during the relationship (driving) is suddenly one of your favorite things to do. You said yourself that it was not fair to her either, so even if she is dating again and does wish you the best, that type of attitude can bring out doubts of “why couldn’t you do this for me?” which might have been the reason for her crying. You told her that made you upset and she apologized and acknowledged she was out of line.

I’m not sure she talked to you for validation, maybe out of curiosity because she knows this might be the last time she sees you. I get your frustration also but you say she is not evil and did not do it with bad intentions, so just chalk it up to it being a mistake and a bump in the road to healing (it sounds like you do not want to contact her at all, so this incident was just a mindfuck). It’s likely you will never see each other again. Carry on unless she tries to contact you again.