Elena's apartment is indeed a gem in the middle of Athens for a couple. We had an excellent stay and would come back again.
The apartment corresponds exactly to the photos and has everything you will need for your stay. We found the apartment to be very clean and modern. The location is excellent since you are 1min away from the Plaka district and 5mins away from the Acropolis. There are plenty of restaurant nearby to choose from. The views from the two balconies are amazing (Acropolis and Lycabetus hill). There is also a direct metro line to the Airport 5mins away.
The communication with Elena was also excellent and quick.
There is also a great cafe downstairs (Victory) whose owners took great care of us: the food was freshly cooked and delicious and the welcome was always warm and genuine - we went there quite a few time