Isabelle is very kind and I enjoyed my stay at her place immensely. The best part was the apartment's location... it's the best neighborhood in Madrid, I think. She cooks a wonderful breakfast, and it was a pleasure to talk to her.
Her apartment is quite big: you will have a lot of privacy. There is a private WC for you, and you will use her bathroom for showers. There is a bit of noise in the room on weekend nights, but closing the windows helps.
I would definitely stay again!