We (my wife, myself, our 15- and 12-year-old kids, and my brother) had an excellent experience staying at Monica's apartment and highly recommend it. The apartment has three bedrooms (two that sleep two each and one that sleeps one), one bathroom, a kitchen/dining area, and a living room with a TV and several comfortable chairs. The apartment is highly functional -- everything is modern, clean, and in good working order. It's just an easy, pleasant, and comfortable place to stay.
We loved the location, which is on the southern end of the lovely Gracia neighborhood. The surroundings were active but not overcrowded, with plenty of restaurants only a short walk away. We all got transit passes, so whenever we wanted to go someplace further afield, we walked the short distance to the Diagonal metro station.
Monica made check-in and check-out very easy, and she responded quickly whenever we had questions. We would not hesitate to stay at her apartment again the next time we visit Barcelona!