Overall, we had a nice stay at the apartment! You won't find a better neighborhood or atmosphere. It is only minutes on foot from the beautiful Sacre Coeur and away from the hoards of tourists. She had great recommendations and was very clear with instructions on getting in the apartment. The decor is modern and fun, while the apartment will suit every traveler's basic needs (bed, shower, kitchen, bathroom).
Our only slight issue was with the cleanliness of the apartment. It seems that someone does live there full time when it isn't rented out. The closet is full of clothes, the fridge is full of food (and smelled bad), and there isn't much space for personal storage. We also found the bathroom/bedroom to be a little dirty--there was hair on the bathroom floor and some on the bedroom sheets. The bedroom is also slightly cluttered, but it didn't really hinder our stay at all. Also, beware that the rooms are quite small! Definitely not an issue, but we thought it was a bit larger based on images. This place is great for two people, but definitely would be crowded with more.
Despite these slight issues, we still had a wonderful time and would still recommend this apartment to any travelers looking to stay away from crowds and enjoy what Paris has to offer outside of the main touristy areas.