I would not recommend Nadia's apartment. I stayed there with my sister for a few nights, and while it was a nice apartment, the wifi worked about only 30% of the time. When Nadia offered to have someone come look at the connection and we declined, she blamed us for being out of the house and preventing her brother from checking it. She also blamed my phone as being the issue, but it didn't work on either of our phones, my computer, or my sister's iPad.
We would have chosen a different apartment if my sister and I had known that the wifi only worked 30% of the time. It's a bit unsettling to not have access while in a foreign country. Nadia should have stated the issues so that we could've booked a different place. Then when I requested partial refund, she sent me $16 and ignored my messages thereafter.
I've had great success when booking Airbnb's, but I would definitely suggest choosing a different Airbnb for your stay in Florence.