Had she ever visited any of the other apartments? Would she know which ones to go to?
She went upstairs to the Payne's apt, as witnessed by one of the cleaners:-
http://www.mccannpjfiles.co.uk/PJ/FATIMA_ESPADA.htm*snipped*
She states that this took place on Sunday 29th April, just before she finished her morning work shift (13.30) as she had the afternoon off that day. At about 13.15 she went to help her mother, who was cleaning apartment I of the same block (5) situated on the first floor. She clearly remembers seeing the girl accompanied by her siblings and mother leave their apartment (5 A) and walk to the stairs leading to the floor above. She was very close to them at a distance of about 1 metre, observing their movements for a few moments because she was charmed by them. Madeleine led the way with a plate (perhaps plastic) in her hand bearing a piece of bread. As regards the clothes she was wearing she only remembers a skirt but cannot recall its description. She noted, because she thought them nice, the type of shoes she was wearing, tennis shoes, light in colour she thinks, which had little lights along the soles, which lit up each time she stepped on the ground. Her siblings followed behind her, wearing the same king of shoes and each holding a piece of bread in their hands, their mother followed behind them without holding their hands. She seems to remember that the mother was also carrying a plate. Moments afterwards, perhaps the time it took to close the apartment door, the father came out and also headed to the apartment upstairs. When asked, she does not remember whether the father pulled the door closed or locked it with a key.
----------------------------------------------------------------------------------------------------------------------------
I would think Madeleine would have been aware at some stage during the week who was staying right next door.