We stayed at Kalliope's place for 3 nights and we really love it! Her place is just a few mins away from metro station and tram station.
She is a really nice and friendly host that even prepared some food for us before our arrival. Also, before our stay, she was kind enough to contact the hotel owner in Santorini for me that couldn't speak English.
We will definitely stay here again if we have a chance back to Athens! :)