I'm trying to catch up on all the posts, and was hoping to get through them before I saw something I wanted to reply to.
I'm seeing this a little differently. In some of those photos of Mariah's party with the doll, she looks terrified someone's going to take her doll away from her. I can imagine a scenario where she's often punished by having her dolls and teddies taken from her. It could just be relate to sibling play where they fight over toys and sometimes break each others' toys. It could be that her toys are taken from her and thrown away if either KW or EK get annoyed with her. It could be that I'm seeing things or seeing the wrong thing in it.
I know when I was very young, a year old, I had strong empathetic feelings for my mom's emotions. That description of knowing how to make your day brighter makes me think of a child who's learned to use that empathetic sense to not just read the emotions but also come up with the answer that if she can keep people happy, they're less likely to turn on her. Babies learn very young that if they smile at someone they'll get a smile in return, so I would say it's an extension of that, but possibly amplified in Mariah if she's noticed that if EK/KW aren't smiling, then she and her brothers are more likely to suffer.
There were some comments before the post I've quoted about the possibility of KW murdering her own daughter as a vindictive punishment directed at someone else? I'm not seeing that in this case. I think that not only is that more often a male preserve, but that also it more often seems to happen at the time of the break-up of a relationship or a crucially difficult part of deciding custody, or perhaps where the custodial parent has a new partner ...I suppose what I'm saying is that I'm not seeing a *what's the word?* the thing that's the straw that breaks the camel's back? I can't think of the proper term for it, but I'm not really seeing anything obvious from KW's side.
And also I go back to the NG interview with the bio dad, and the description there was of Mariah waking, crying, getting hit, being hurt so badly that she was near death/dead. It seems more reminiscent of the van getting attacked by EK in an episode of violent petulance for not getting his own way, but this time I think Mariah got the attack that the van received before. I guess they'd had a long drive back, not arriving home until 11pm or so, he might have been ready to put his feet up (maybe with drink or drugs), go to bed, maybe KW is in the bath or unpacking and so EK goes to tell Mariah to go back to bed (just like KW's original story) except that it didn't end with Mariah going back to bed, it ended with Mariah getting beaten to death.