This place is good with a couple of warnings.
Irene's flat is very well located. It is a walkable distance to Santa Croce Square and Duomo. The streets below have lots of restaurants and bars. She also gave us a good tour of the flat with lots of information of the surrounding area.
The place itself is nice. It is dark and quiet at night and we all slept very well. The flat is not handicap accessible because it is up 2 flights of steep stairs.
We had some issues with the shower. For instance, the shower curtain is completely ineffective at keeping water off the bathroom floor, as it is too short and not well installed. Another problem is that the bath mat is just a towel and doesn't soak up water very well. A simple bath mat and properly long shower curtain could have fixed this. The toilet in the half bathroom is also thunderously loud. I don't recommend using it if you want to avoid waking people up in the middle of the night.
Lastly, we had a late flight and we weren't allowed to store our bags past checkout so we had to store them elsewhere. She gave us a taxi number to call for us to take the bags to the Santa Maria Novella station. However, the number she gave us was for a taxi company that didn't operate in the Santa Croce area. Therefore we had to go to Santa Croce Square to wait for a taxi and it took 40 min to get one! I don't know if she was misinformed, but it was sort of infuriating to be given false information.
Overall, we enjoyed our stay and had a wonderful time in Florence. The flat was very well located, and easily walkable. However, be wary of the poor taxi coverage in the area. I hope Irene fixes the shower situation.