*** The following is my own pure speculation only about a possible sequences of events that could explain why someone might hide an accident***
***I am not suggesting that this is how the FFC felt or acted, nor that she is guilty if any crime***
Imagine a hypothetical professional person who is successful, with a good reputation, who is entrusted by others to look after non-biological children. This person likes things neat and organised and cares about things like efficient and timely repair of household goods, making sure that children in their care eat well and always brush their teeth before bed (even when arriving late at night to an away-from-home destination they are going to stay - instead of just letting them go to bed), that these children have a beautiful home to live in, go on nice holidays, have an abundance of toys, this person even makes story boards of the children with lots and lots of videos and photographs etc etc. This person likes others to think well of them and wants to think of themselves as doing a really good job of looking after the children (and convince others of this as well). They also really want to have a family of their own and have waited a long time to create one. They are invested in creating the Insta-perfect/ Facebook happy family image.
Imagine that this person, being tired from a long car trip the night before, then getting up early with the kids, struggling with a boisterous child who is being demanding about what clothes to put on, then gets distracted doing something inside while the children are playing outside. This person then suddenly realises that they haven't heard one of the children in a while, and, feeling bad about not being attentive, quickly goes off to find the child. But instead, tragically, they come across a lifeless child who has been in a terrible accident. This person is used to being in control.
They gasp, one hand flies up to the mouth in horror as they swallow their scream. This person knew that they weren't keeping a close eye on the child and now they feel completely responsible. Oh my goodness, how will the person ever explain this to anyone?! And now, because they know they *should* (in their minds) have been more attentive and are potentially to blame, the other much-wanted child might be taken away from them! Panic ensues "OMG! What can I do? I can't let anyone know about this!". In their panic, in a bizarre spur-of-the moment decision, the person decides to hide the body of the child - so the sibling doesn't see the body, so the partner won't know what happened. This person has a lot to lose if people think the child perished on their watch.
Then, when the partner arrives to the scene, the person tells the partner that they can't find the child! The partner tells the person to call 000..... and it all snowballs from there.
This doesn't seem to make any sense to most of us. Many of us would scream, call an ambulance etc etc. But some may not scream, and in the heat of the moment, when stakes are high and thinking clouded by guilt, self-preservation and thoughts of protecting someone else (like another child), some may do things that ordinarily wouldn't make much sense. It doesn't mean that they are a sociopath/ psychopath/ cold/ callous. Just panicked and not thinking right. And then when once the lie starts it gets very, very difficult to come out later and tell the truth - especially knowing that it would bring the judgement and wrath of millions of people.
***Speculation only***