This is an amazing apartment and we highly recommend it to others: Full of charm and nice design elements. It has two living rooms (one with the kitchen), a bedroom and a bath. In addition we were surprised that the apartment has two big balconies with afternoon sun.
Although we didn't get the chance to meet Elsa, she took good care of us. It was no problem getting the keys and finding the apartment with her instructions. The apartment is located on the east of Montmartre and we used 5 minutes to walk to Sacre Coeur. The area further east for the apartment may to some seem a bit unpleasant, but we took the metro from this area every evening and never felt unsafe.