From my experience of having an ex who for a long time was absolutely inflexible about changing the schedule to accommodate my work, I learned to bend work around the schedule. So I left for work trips a day late, returned a day early, and in one supposedly fun thing I will never do again, traveled to central Asia on work and returned within a week.
If you're dealing with an unreasonable person, it's useless to try to reason with them. And if they are not obligated to do something (like change the schedule by a day or two to accommodate you), they will not do it, so it's useless to ask and then get upset if they don't respond. Unreasonable people do not understand reciprocity ("Dad was flexible when I needed some extra time this summer so I'll be flexible now"). They do not grasp the concept of what-goes-around-comes-around.
I would chalk this one up to experience and let it go. Yes, your ex could have helped you out by rearranging the schedule, but she didn't have to, and so she didn't. If you expect your ex to behave the way you would behave in a similar situation, you will drive yourself crazy. Your work schedule is going to have to flex to accommodate your parenting time, not the other way around. It sucks, but until your ex gets a personality transplant, that's the way it will be.