Manuela's place was very convenient for us.
It is very easy to access from the metro right from the airport. We met Manuela outside the main doors and she took us up to the apartment. There was a festive cake (popular around Christmas and New year's) waiting for us. She showed us the apartment and set us up with everything we needed (wifi, etc.).
The elevator is a bit tight for 3 people with luggage.
We walked to the Colosseum, but some might find this walk far. It's about 30 - 45 min. The area itself feels very safe and there is a market /grocery store 2 min from the bnb with everything you might need. The only issue you might have is the local kids setting fire crackers off in the back alley late at night, but with the doors shut it didnt seem to wake us.
We were here on New Year's eve and the fireworks show from the balcony was awesome. What a great way to take in the new year!