Would highly recommend staying with Carla. She is very warm and welcoming and her apartment is beautiful. She does not speak any English, but this is not a problem as you can communicate through interpretation apps on your phone.
The apartment is around 25-30 mins door to door to the main attractions in Florence. Although not a problem for me, it does make it harder to come back in the middle of the day and go out again as you lose 1 hour minimum on the journey. However, the location is great for local food and it is a lovely and quiet neighbourhood.