I agree that the child does not really understand the concept of death but seriously I don’t think that adults do either. So I think you should allow the parents in a case like this a little self-delusion of the child’s choice to end her own suffering.
Essentially the parents have been trying to prepare their child for death and have decided that their child should die at home rather than endure a prolonged and uncomfortable death in a hospital. I see no harm of any kind in what they are doing.
Personally I admire their courage. It may have been better if they had kept this private but I suspect that they thought that their decision would be universally supported by their on-line group.
Well put.