I spent one night in Shelley's appartnet and it is perfectly located for such a short trip. A lot of the main sights are in walking distance. Unfortunately it was very windy that day and the roof top terrace was not a welcoming place but it must be great on a sunny day.
Shelle is a wonderful host, she gave me good tips what to see and where to eat. I can strongly recommend this place, if I will be in Vienna again I will definitely check if her room is available.