Firstly, what a jerk. Secondly, I know from past experience that trying to convince someone and/or get them to change their feelings is futile and you have no need to justify yourself to her - whether it's for your benefit or hers.

I would keep your thoughts on the big picture which is sorting out maintenance/access and don't get distracted by her because her thoughts/feelings are immaterial to that situation.

If you can't help yourself (I mean that in a nice way), I just wouldn't spend time outlining all the whys and wherefores but just send a really, really simple one-liner along the lines of, "just remember that in life there are two sides to every story and you're only hearing one."