Her hunch was correct. Flak (of Flak & Shrapnel's) was on hand with plenty of ammo and expertise. She was able to trade all of her .32 and flamer ammo (for which she had no use) in exchange for almost 1000 rounds of 5mm minigun ammo. Certainly a start! Flak couldn't make any promises, but he was willing to take a crack at her minigun if she brought it by. That would be an extra trip, but potentially well worth it.
Rivet City. 101 was impressed. While she searched out Bryan's aunt she passed a church. Not Children of Atom, but one which worshiped a Saint Monica.
There was also a museum. The curator still in need of the Declaration of Independence to complete his collection of historical documents. He promised it would be "well worth the effort" if 101 could find that for him. She promised to bring it to him if she came across it.
There were several places that were closed or off-limits, but fortunately 101 ran into Bryan's aunt Vera in The Weatherly Hotel (a hotel!) while inquiring about a room for the night. Vera was saddened by poor Bryan's plight and more than happy to take him in. Vera actually runs the hotel in Rivet City so she has both the space and the means to care for young Bryan.
After a very restful sleep on the most comfortable bed since the Vault, 101 nearly ran all the way back to Megaton to fetch Bryan and her minigun. The return trip to Rivet City was actually fairly pleasant with a companion. They even ran across a handful of radroaches that she allowed Bryan the honor of decimating with one of his Nuka grenades. He enjoyed that very much; of course 101 felt the need to caution him against throwing them around Rivet City. When they arrived Bryan and Vera took to each other quite naturally. Seeing them embrace each other made 101's heart happy, and also anxious to be reunited with her own family. She excused herself, promising to check in "as often as possible", and returned to Flak with her minigun. As Flak tinkered about with her minigun his partner, Shrapnel, marked her Pip-boy map with the metro tunnel entrance she'd want to take to get to the GNR building as easily as possible. "You'll pop out right near it this way". Flak was able to make her minigun useful, but not terribly sturdy. "It should be able to handle the ammo you have, but not much more before it breaks again. Sorry". That would have to be good enough. She thanked them both, paid for the repairs and headed out for her first venture into the "overrun with Super Mutants" DC Ruins.
Well, either Shrapnel was in cahoots with somebody or very good with directions. Since 101 couldn't fathom somebody using the Brotherhood of Steel emblem as bait, she thought it safe enough to enter the metro. She was further encouraged when her biggest obstacle was a handful of ghouls along the way. There was one Super Mutant, but it was previously injured (possibly by more ghouls) and didn't pose much of a threat. She became a little nervous as she reached the exit gate into DC and pulled out her minigun before going through.
So this is the DC ruins. A section of it, anyway, and there's the Galaxy News Radio building right in front of her. While she wasn't immediately bombarded by Super Mutants, 101 hoisted her minigun and headed for the last known destination of her father.