The flat is very spacious and sunny, super clean and generally has good vibes. Charlotte is friendly, helpful and welcoming, though she had somehow forgot to mention in advance that the room does not have a window - neither is it shown in the photos or description of the room. Instead, it has a milky glass "window" in the wall touching the bedroom next to it, which barely permits the sunshine to enter (but perfectly transmits the sound) - this brings problems with the room air quality and privacy in both rooms eventually. Otherwise, the flat is beautiful, close to 5 and 7 metro lines in lovely 19e arrondissement.
Overall, I enjoyed my 3 months stay despite the mentioned problem, which I hope will be solved or notified in advance by the owner since the owner provides a long-term accommodation and spending the summer in a room without a window can be a disappointment, resp. the price of the room is inadequate.