We - young couple, mid-twenties - can fully recommend Dani's apartment. The communication with Dani worked great from the beginning, Dani never took longer than an hour to answer (usually only a few minutes). The apartment is very spacious and you can certainly stand it well for four. Everything was lovingly furnished and very clean. The location is perfect, you can hardly live more central in Florence. But the highlight is definitely the terrace with a unique view of the Duomo: we often just bought a bottle of wine in the evening, enjoyed the view and listened to the voices and music from the square below. It doesn't get any better than that :)
Also, be sure to ask Dani for recommendations for restaurants and things to do - she sent us a long list right away and really every recommendation we tested was a complete success!
The only thing you have to be aware of: There are about 90 steps leading up to the apartment, which can be exhausting after a long day of exploring the city. But the effort is immediately forgotten as soon as you have the magnificent view in front of your eyes again.
We have visited AirBnBs many times and agree that this one was the best so far. We will definitely come back again!