We had a very nice stay in Anabela's flat. The main quality is its location, which is absolutely great. Near the subway in Malasaña, in a lively, young and hip area, with lots of charming bars and shops. There's a lovely square just 2 minutes away from the flat and we spent there many moments, enjoying sun and Madrid life. The flat is completely renovated and very clean, we'd certainly recommend it for a short stay, if you're mainly looking for a place to sleep and shower (great shower btw).
If you want to spend more time indoor, note that the place is very minimal (no table or couch) and there's almost no daylight.
We didn't meet Anabela but she sounds charming and her neighbour Loly is very kind and helpful.