We had a great stay at Malu's place. Malu was there when we arrived and had filled the fridge with food and drinks. Malu was very nice to inform us about the neighbourhood, places to see and where to go out, we couldn't ask for more. During the stay she replied us very fast when we had questions or doubts.
During our time in Rio we did not feel unsafe in the area around Copacabana and the apartment is nicely located in terms of public transport too.
All in all a very good experience. We'll definitely consider staying at Malu's place again if we go to Rio.