Sofia is a friendly host and Barcelona is a great city!
If you want lots of restaurants and bars you may prefer to be in Born, El Raval or Graçia but Sofia's apartment is very close to Sagrada Familia and good metro stops.
The apartment is a good base for short stays, but if you're staying longer you might want to find somewhere with a bit more light and space, and where the amenities are a bit more up to date.