The apartment itself was cozy and comfortable. There are nice restaurants and coffee shops close by, and charming alleys in the Alfama are just around the corner. Sandra was a lovely host and was very willing to accommodate any requests (she helped us coordinate an urgent delivery within the first few days of our arrival). Unfortunately there were some issues with the apartment, but they are unrelated to the apartment itself or with Sandra.
The exact location of the apartment is in a particularly grimey alley. There was a constant smell and presence of human urine and feces next to the outdoor trash cans in the alley along the side of the apartment (not in front of the main entrance). There was also a building along the side of the apartment with scaffolding that was occupied by homeless people who would climb up and down at night which was slightly uncomfortable. Fortunately, you can close the blinds so that nobody can see into the apartment. Ultimately I think the apartment is fine for a short stay. We spent about two weeks there which probably made these things more noticeable.