People make this decision all the time, and sometimes go for the more expensive option. Size of the schools is not the same. Some want the religious aspect of the school.
We have a very desirable public high school just a few miles from me. It’s in a wealthy suburb. Some people choose to move to that district (and specifically that school’s zone) just for that school, or try other ways to get in like using another address, renting an apartment - those things don’t work. It has about 850 kids per grade, offers almost 30 AP courses, 5 or 6 foreign languages, all the science and math classes you could want. It also has every sport and sends about 100 athletes per year to colleges, many with full scholarships. I know it has GC just for athletes and other that are very knowledgeable about top 20 admissions. It is the country club of public schools.
And yet some parents send their kids to the two fancy private schools in the area @$35 grand per year (and I know others send them to boarding schools that cost even more). Why? the other schools have graduating classes of 100-150, even better sports facilities (although not more competitive teams), have the fit and feel these students want.
Still other parents split the difference and send their kids to the private catholic or christian high schools at $15k to $20k. Nice schools, about twice the size of the elite privates, but more competitive in sports.
Why are these parents spending $15k to $35k when there is a perfectly good high school down the street with many more classes than the smaller schools could ever offer? That’s how they want to spend their money. They may think those private schools are a better size, a better fit, for their children. Sometimes it’s because that’s where the kids want to go because their friends from the riding club or ballet are going there.
And some parents do both. John Elway had 4 kids and I think 2 went to the public school and 2 went to the expensive private school.
My own kids would be going to UMD for free because that difference is too much for me to afford, and my kids love a bargain as much as I do. The OP said she can afford it so that family has the luxury to weigh their options.
OP, is your daughter wanting you to make the decision and ‘force’ her to UMD? Can her sister throw some info light on the situation, like that she’s so happy she has her pot of money for grad school and how many of her friends are limited in their next step, either grad school or career wise, because of spending their 529s (or loans)?