The apartment is very conveniently located - i.e. walking distance to Sagrada Familia, large grocery store in a neighboring building and a restaurant at the ground floor of the building. Subway and Renfe lines are within walking distance. The area feels safe and the apartment is clean and cosy, although slightly noisy due to close proximity of a busy street / highway. Although it was not a problem for me, if someone is an extreme light sleeper the noise can probably be an issue (especially in summer when one needs windows to be open for 24h :)).
Judith is a great host - very helpful and willing to answer lots of questions, but also respects privacy of the guests.
I definitely recommend Judith and her apartment for stays in Barcelona!