We had a nice stay at Monica's apartment. It is very well located : at a walking distance of the Gaudi beauties (Casa Battlo, Pedrera and Sagrad F), neighbordhood is cool. There is a supermarket "Suma" in front of the building and you have an organic supermarket Veritas also (5 min walk).
Passeig Gracia is very close to have dinner and a walk after...Try the El Nacional restaurant.
The apartment is located in a very quiet building and typical, it is clean and well decorated. You have all what you need to cook in the kitchen. We did not have any direct contact with Monica but all the person we were in contact to, were very friendly and super efficient.
The only thing we have to say is that the double room, is pretty noisy. We use ear plugs to sleep well.