Lena's apartment is a great place to stay in DC! It is clean and comfortable, with plenty of space for two people to crash at the end of a long day out. We ended up cooking breakfast most days (Giant Grocery and Whole Foods are a 2 minute walk away). The neighborhood was quiet at night and felt very safe. I recommend checking with Lena on food recommendations, because she gave us a massive list of places to check out, and the couple we did were perfect for what we like to go to. H Street has a trolley that can get you up and down the street at night if you are uncomfortable walking.
It took maybe 15 minutes to get to The Fox Den from Union Station, and it was only a 35 minute walk to The Mall. So for us, it was perfect since we like to get out and walk or explore.
The washer and dryer work great, so you could easily pack for fewer days than you'll be there if you can time some laundry into your trip. It came in handy for us since we had a lot of rain and needed to dry our clothes.