My daughter lives in Crown Heights, and she is on St Marks Ave too! But in an older building, not new construction. It is a pretty decent neighborhood, she moved there from Harlem a few weeks ago. It is a longer subway commute into Manhattan where she works, but not bad at all, half an hour tops. It takes longer to drive there in your car.
I would not call Crown Heights gentrified, it is very mixed. Even the part of Harlem where she lived was mixed, some nice building and stores, then one block over, old and sketchy. It's NYC, you get what's available unless you can afford a lot of money for rent or are willing to share small apartments with several people.
When you are young and twenty, it's a great place! I'm fifty-five and and love my open spaces and a car in the garage.
Good luck to your daughter, she's smart enough to finish medical school, she will manage Brooklyn just fine.