Wise, bright and expressive person, Charlotte is one of the best hosts, I've encountered on my journeys. I would even say that I've made a good friend thanks to Airbnb. She is hospitable, kind and was also incredibly helpful when it comes to suggestions and tips about Rome.
When it comes to apartment, this is a proper old Roman flat: huge and full of stuff that has it's own stories to tell, breathing with life and history. Neighbourhood is in center of Rome yet quite and comfortable. You can (and should) walk to most of Rome attractions and interesting places by foot. A lot of good food for any budget around.
Overall, if this place is free, don't hesitate and book it. Oh, yeah, and don't forget to get a gelato, when you'll be in Rome.