I have stayed with Marcia for the last month, and my experience could not have been better. Marcia and her daughter Tainah are very friendly and welcoming, and are excited to have people from different parts of the world stay with them. Both Marcia and Tainah speak English well, and are happy to practice Portuguese with their guests.
The room is large and very comfortable with lots of storage space- bonus points for the veranda with hammock where you can sit and look out over the hills. This place is best for people who are looking for a quiet place to rest, relax, and study, because it is not down in the hustle and bustle of the main area of Botafogo, but about a 15 minute walk up a steep hill from the subway, bus lines, grocery stores, bars, and restaurants. This means that it is quiet, and also cooler than other parts of the city. I highly recommend staying with Marcia, she is a great host!