The apartment was a great place to stay. It is modern, recently renovated, very clean, equipped with every thing you could ask for, spacious, and walking distance to all major sights (although be aware: Sintra itself is not a very pedestrian-friendly place, due to the steep slopes and the lack of pedestrian paths on most roads).
Rita was a very friendly and welcoming host: she took great care of our needs and demands (as we were traveling with our little boy this was really appreciated). If we will be back to Sintra we will definitely stay at Rita's apartment again.