Marian es super amable. Although I was unable to meet her, she made sure she was in constant contact and that I could just message her if I needed anything.
At no point did we need anything - the flat is fantastic. The beds are very comfortable, the kitchen is well-equipped, the bathroom is great and the living area spacious. The location is perfect - you can walk to the Royal Palace and Puerta del Sol. There are also lots of lovely bars and restaurants in the neighbourhood, so you don't have to stray too far if you don't want to.
I'd wholeheartedly recommend staying at Marian's cosy flat, it's wonderful and Marian is a great host.