Davel as just pointed out about context,English in the interviewee's second language,imo she means just what she says that "wouldn't Madeleine be able to go looking for them".
Yet the translation transcript gives us a more confusing statement ""SF Did it ever cross your mind, Madeleine wouldn't be able to cross the door just looking after you, alone?"
Yet to me it seems that she is asking a different question "Did it ever cross your mind" or "did you ever think" "Madeleine wouldn't be capable of using the doors on her own in order to come looking for you?"
Plenty of discussion on the forum over the years as to whether Madeleine had enough height , weight, strength etc to be able to open the doors and or gates on her own.
In fact it was a question being asked and your translation is not a question. "wouldn't Madeleine be able to go looking for them" has to become something else as it has to be phrased as a question.
Being able to wake and wander is dependent on Madeleine being able to open a door in the first instance.
If she can't open a door would she resort to opening the window and the shutters?
I imagine a 4 year old being able to be trained in how to open the shutters but there has been no such training given to Madeline AFAIK.