Mirta's apartment looks very much like the photos... it's a quirky, fun design. The owner has made the inside look and feel like the inside of a ship, which is very cozy. Everything works well, and the kitchen is very well equipped with lots of pots and pans, utensils, etc. and basic spices/oils. She packs a ton of storage into this space!
Beds in both bedrooms were comfortable, and we had enough linens. Bathrooms were clean. As others have mentioned, you'll need to climb three flights up, and the apartment itself is full of levels, including in the upstairs bathroom. You kind of have to watch your step! The upstairs bedroom is on a platform, and you can easily sit on it but an adult can not stand up without hitting the ceiling. This is all gotten used to quickly, and part of the fun.
The neighborhood is amazing for walking around, with lots of cafes, bars, and restaurants. You can walk to most major attractions, or hop a bus. It's also a five minute walk to Campo Di Fiori for shopping at the market and the terrific surrounding butcher shops and bakeries. Very near the apartment, I recommend La Renella for pizza, bread, and pastries. And the cafe right below the apartment, Checco Er Carettiere, is good for coffee and a quick pastry. We liked the restaurant owned by the same people and right next door as well--hearty, Roman food.
One thing to note about the exact location of the apartment: there is a square right below and two popular bars a few doors away, so people are partying and playing music well into the night on most nights. The noise is distracting in the living room if you plan on spending lots of evening time there reading or watching TV. Bedrooms remain quiet.
As a host, Mirta was very helpful during the reservation process, even arranging airport cars for us that were cheaper than taxis or Ubers. She was not present during our stay, but her colleague Joy helped to get us set up. During our stay she as also responsive, but sometimes needed a half or full day to respond to questions.