Why no answer to her heartfelt letter.
And why would she write such a pleading letter to him if she was guilty of what many sceptics believe.( Not you)
There is indeed plenty of pleading for sympathy, but what does she want? She wants specific information. What work is being done to help find her missing daughter? She goes on to mention that moment when she discovered that Madeleine had been taken. She then says "It would be good for Madeleine if we could all work together to help find her and the person(s) who took her."
She has left Rebelo in no doubt that she, despite being an arguida, is sticking to her story. Whatever the investigation has thought or is thinking she is saying that Madeleine was abducted and that the PJ should be looking for her and whoever took her.
She appears to be accusing the PJ of a couple of things too; "This shouldn't be about "finger pointing blame" nor should it be about differences in culture."
She then makes a claim that the PJ may not agree with; "We will continue to work with the PJ (and we are keen to do so as soon as possible!) as we have done since that moment when I discovered that Madeleine had been taken."
If the PJ don't agree with her abduction story and are not searching for a live child they can't tell her what she wants to hear. Judicial secrecy forbids them from telling her what else they might be investigating, so the letter is unanswerable.