I would say this is more than possible in many cases, but I don't think it's the way it is in this case.
In my experience, a 7 year old would stay with the parent that provides stability, at least in their minds, not to take care of the parent unless they had to. Emily's daughter does not need to take care of her dad, her mom does that and he doesn't go on many family outings.
I know, I'm off base replying to this post, but I'm doubtful about the scenario you posted.