I hated living in DC. It was expensive and difficult. When I lived in Southern California it was rather expensive and difficult, but I figured that was my price to live in really good weather. What was I getting out of living in DC? Sure as hell wasn't good weather. Access to government? Bleech.
To each their own. One thing that DC DOES have is a much more "international" flavor population-wise. I've lived in a number of other places (including the state you live in), and not found quite the same flavor. NYC, LA, Miami, and a few others come close - but Washington with the number of embassies and transients stands out in it's own way.
YMMV.
I think the OP's daughter is making a truly giant mistake. Last I heard you could go to law school in Minnesota. It's beautiful. Yeah, its cold. Put on a coat, buy a good hat. I know, young people have to make their own mistakes. But no m after where you go, there you are.
Full disclosure: I did my B-school at GW. Part of the reason that I did was the number of international students that attend. I wanted the international exposure. GW Law, like their international studies program stand out. And being in DC gives access to more lawyers than many other places (which, of course, is both good and bad). I still mentor students and entrepreneurs at GW, and still find a heavy international presence. From my view, that's good. For others, it may not be. Again, YMMV. Good faculty in Law, too.
BUT, whether that's necessary depends on the long-term career choice. Plenty of good lawyers - including some on this board - that earned their degree from other institutions. It might be the right thing for her, or it might not - we're not in a position to tell that. If her goal is policy work, this is the place to be.
As far as DC advice, live close to the metro if you have to go downtown, as close as you can get.
I'd amend that. As a young person, she'll find more people her age (and more things to do that are attractive at younger ages) living in DC itself (Foggy Bottom, Adams Morgan, Woodley Park, Cleveland Park, DuPont Circle, etc), Arlington, Old Town Alexandria, Falls Church, Bethesda, and the College Park areas. Parts of the City of Fairfax, and places along a couple of the Metro lines also have bars and activities that attract the younger crowd. Ashburn, Gaithersburg, etc. are too far out for socializing and nightlife. And a better chance of finding compatible roomates living close in. The subway can suck (insert your favorite pejorative here), and is still working on rebuilding, but when it works it can be convenient and faster than taking a car (or Uber).
Also note that there are a few areas close-in (NOT ones I mentioned above) that are "challenging" crime-wise.
DCA is a stop on the subway, BWI is a stop on Amtrak and MARC rail, and maybe someday the metro system will go to IAD (latest issue: problems with the concrete that contractors poured).