Other reviews have mentioned the smallness of this space, and they aren’t wrong - take what you’re picturing as “small” and probably reduce it by another third. For example, I am 5’4” and wear a size medium in most everything and I don’t think a person much larger than I could comfortably get into the shower. Further, when the bed is down it fills the entire space and must be put away in order to open and close the door, which I didn’t realize when booking.
That said, the location is amazing. Very short walk to the metro, and the RER (train) line is quite close as well. Getting around Paris was wonderfully easy from this apartment. Further, it is right next door to a beautiful Parisian bakery, so we had a great time grabbing pastries for breakfast on our way out. I was traveling with a group, just two of us saying the nights in the apartment but five of us in total who used the apartment as a mid-day drop-off place for suitcases, shopping bags, to get a water bottle, etc and it was not particularly well-suited for that (suitcases for more than one person make the room feel a bit claustrophobic), so if you have similar intentions, I’d look for something with a little more breathing room. But if a smaller space works for you, the location is unbeatable, very clean, and Marie-Alice is one of the most communicative and helpful hosts I’ve ever had!