So what? Yes people are richer, more gifted, more athletic than others. Can't we celebrate an achievement because not everyone can do it? All Olympic athletes have exceptional genetics and most people simply can't stand a chance no matter what they do. And most of them are not poor either, does it undermine the achievement?
And it is not that much money. Clearly, it is not for the poor, but it is something achievable for the upper-middle class in North America or Europe, you don't need to be a billionaire for that, not even a millionaire. Yes, flight lessons are expensive, but we are talking ultralights here, not jets, a flight hour is less than $100.
As for the the "self-congratulatory copy", that actually makes the accomplishment even better. Really rich parents could have just bought a plane and hire a few guys to plan for everything, register the record, done, the "rich kid" would only do the flying. She actually had to look for sponsors, set up a shop, and actually build something to finance the trip, it may even become profitable. It is not just a trip, she is essentially building a company and a personal brand, and while Zara obviously gets a lot of help, she is still at the center. Very impressive for a 19 year old, even with "rich parents" helping her.