We've stayed at Ada's place for three days and really enjoyed it.
The location is very central: just around the corner from the Dome Square and about 7 minutes’ walk away from the central station. There's also a grocery store not far. The flat has everything you need, including a kitchenette.
We haven't met Ada in person unfortunately, but she was very helpful in her messages and quite prompt too.
She's also left a notebook with dining and shopping recommendations - hand written with lovely pictures :), we've tried a number of them and they all proved to be really good.
Would definitely recommend this place for those visiting Florence, we loved our stay.