On 5th May the PJ descended on Luz and did a house to house. Did they visit Mrs Fenn? We don't know so we can't say 'they asked her nothing'.
If they did visit she didn't mention anything to them or she would have been interviewed. There was also a command post in Block 5 where she could have gone and spoken to the police.
The blame for her late statement can't be laid at the PJ's door unless we know a) if they visited her and b) what she said if they did. She also had the option of approaching them if she thought she had relevant information.
We visited 443 homes, some of which were occupied as the inhabitants of those respective homes were questioned whether they had any information relating to the disappearance of the child, Madeleine McCann or if they witnessed another situation and/or suspicious activity during the dates preceding the events;
In the case of an affirmative answer, these witnesses were taken for formal questioning related to the investigation;
http://www.mccannpjfiles.co.uk/PJ/EXTERNAL.htm
No doubt. However, Mrs Fenn's statement was given four months after the event. Nor can I find any police statement attributed to Mr and Mrs Moyes who were not only resident in the apartment above Mrs Fenn but who actually went out and searched for Madeleine.
Apparently they were asked nothing about the night of the 3rd by the police. Nor were they asked about their search activities. They gave detailed accounts to the media ... had they been interviewed by the police that would have been said.
I believe the adage in a missing child situation is to start at the site and work out from there. 443 homes were undoubtedly visited it seems no-one bothered with the occupants of Block 5 ... for example ... does anyone know who occupied the flat with the rotting food in the open fridge which excited the attention of the GNR dogs?