@Kitcaterpillar do you not realise that the 'text' conversation is a condensed version that took place in person, and that we're getting via Harry, who wasn't there?
As such, we don't know the tone in which Kate or Meghan was talking, or what else was said, including anything helpful Kate tried to do. It sounds like as Meghan didn't get back to her for 24 hours, she did try to do something by asking a designer about what to do about the dresses; that could have been intended to be helpful. We know that the problem was Charlotte's dress was far too long and big, so clearly something had to be done to stop her or anyone else tripping over it down the aisle.
IMO going by the exchange, both women were snippy and rude, but both had stressful life changes going on. In the mock up text, Kate responding with "fine" (when clearly she would have said more in person probably) had me laughing, sounded very like my teen daughter.