My $0.02 - there is no such place that's convenient to both Bolling and Dulles. It'll just be a matter of the least inconvenience. Sorry.
Arlington and Alexandria don't have gang problems. I'm not sure where you heard that, but I spend 90% of my non-working life in those two areas and it's perfectly safe.
I would honestly say Alexandria. It's right across the bridge from where 295 intesects 495 so your commute won't be bad - although you'll cross the Woodrow Wilson bridge so there WILL be traffic. (My #1 rule with this area is: don't put a bridge between you and work, but I don't have a daughter's safety to think about.) Alexandria is relatively easy to get to from Dulles, although it is a 45 minutes in easy traffic. Don't let that number scare you; 45 minutes is very reasonable for this area. And since she probably won't be commuting with the rest of us 9-to-5 drones, she won't have to worry too much about the traffic snarls getting from Dulles to Alex. And when she does she can take the Dulles Access road all the way to the Beltway which is much more pleasant than I-66.
Oh, and I'm the Dave who's safe for your daughter to meet.
Will watch for a thread on Dorki.