The apartment is in a central area, a taxi to Castel dell'Ovo is about 15 EUR. We found parking spots in both of the nights we were there but a small car is a must, you can never fit an SUV. The area is typical for central Napoli I guess, buildings in bad shape, narrow streets, immigrants, but it doesn't feel unsafe if you get over the initial shock.
Fabrizia was very welcoming, she greeted us personally and gave good tips for what to do. She replied to any message we sent to her so thank you for that!
As for the apartment: it was clean, we could make coffee in the morning. No sponge or dishwashing liquid, so we washed the glasses with just hot water.
The terrace is indeed the selling point, but be advised it is shared with another apartment, actually it is the only way for the other guests to enter their apartment, so you will meet them for sure. There are 2 tables in there so you will have a place to sit, there's just a chance you will not be alone. The bedroom window is facing the terrace as well, but there are curtains.
Overall a good experience although it was cold outside (3-4 C at night) and the apartment has no heating so it was cold inside as well. We tried using the AC for heating but only the one in the kitchen worked sometimes, they do work for cold air though so I guess they are useful during summer.