My 14-year old son and I stayed at Nina's Capitol Hill area studio apartment the last week of March - prime time in DC. The apartment was very much as advertised, and Nina was awesome! She was very responsive to my communication. Starting with my first message the moment we landed, she responded promptly with exact directions, etc. She was very friendly and helpful. She made it clear I shouldn't hesitate to ask for anything, and she was very available.
She stopped by one night (texted first to ask if she could come by) with locally made gourmet ice cream as a special welcoming treat. With this welcoming attitude, I felt comfortable asking her various questions, and never felt like I was "bugging" her. In the course of the week, I asked her where I could print something, if various neighborhoods were safe to be out at night, etc.
As far as the apartment, we felt the location was REALLY great. It's two blocks from Capitol South metro station; and notably, three lines service that station which made getting to the mall/downtown area super quick and convenient. It's also just 3 blocks to the Library of Congress and the Capitol, and a cute commercial area on Pennsylvania Avenue with coffee, restaurants, etc.
I'd stay at Nina's place, or certainly recommend it to anyone visiting DC.