Gardenia is a lovely host. Her place is really cute, and she keeps it very clean, even with multiple people staying there. The apartment has a beautiful view of the river from the breakfast area. The building itself is very charming.
I just have a note about the location: I was surprised so many people gave the location a five-star rating. The apartment is a 20 minute walk to the *very edge* of the Alfama neighborhood, where the attractions/cafes start to pop up. To get to most places that tourists would be interested in visiting, including the Bairro Alto area where most of the good restaurants are, it's a 35-45 minute walk (you can see this by putting the route in Google). So you're looking at an hour or more of round-trip commuting to and from the sites every day, or double that if you want to go home to rest up at some point and then go back out. This made me feel like I was commuting, which isn't a great feeling when you're on vacation.
Other than that, this is a great place and Gardenia is an excellent host. I think it's a good fit for people who specifically want to be away from the more touristy center, but not good if you're looking to be super close to the sites and good places to eat.