I didn't get a chance to meet Carmen but her son was there to welcome me, and he's a real sweet heart! Very helpful, very friendly and very thoughtful. He was outside the building waiting for me when I arrived, and woke up in the morning to see me off. He also offered to make me coffee in the morning!
The apartment is nice and spacious, with a very nice bathroom as well. It's located very close to Atocha, so it's convenient if you need to take the train, or visit the Prado/Reina Sofia museums. I would definitely recommend this place! :)