Dana's place is very nice located at the top of Katavati with open view to the villages and the sea. It is also nearby the Apollonia where all the restaurants and night life is. There are shops nearby that you can find food and supplies.
The house is as described with bedrooms in the ground and first floor that is separated (i.e. no internal staircase). The kitchen is fully equipped with basically everything you would need to cook.
Dana is very easy to contact and responds immediately. We loved our stay in Sifnos and probably come back one day!