Based on the facts we have of MM - she is very confident, outgoing, chatty, she had a habit of waking after being put down to sleep and going to find her parents, the twins had previously woken her crying on at least two nights that week and knowing the patio door was left unlocked:
If it were me and my niece, and she does sound an awful lot like my niece which is why I'm comparing it, my first thought would be she had wandered off to find me.
Yet we know KM's first thought was she had been 'abducted' and then there are the following two entries taken from two separate witnesses who overheard GM on the phone a couple of hours after MM's disappearance:
Mr McCann was absolutely distraught telling the person receiving the call that he feared 'she (Madeleine McCann) had been taken by paedophiles'.
And from a separate witness:
He said something along the lines of there being Paedophile gangs in Portugal and that they had abducted Madeleine. I was so shocked by this, having originally thought that she had just wandered off.