Are you serious? Putting a heart sticker OVER the duct tape screams MOCKERY, not kindness! Like, "haha, who is the angel now?" This is very good for the prosecution- and the blanket could have blood on it for all we know, and she threw it in there to get rid of it.
Also, any items from the home points to the family. Explain how the defense is going to spin leaving your daughter dead in a laundry bag - taking the time to add hearts and blankets? But not ... calling the police to say something happened?
A kidnapper wouldn't have gone to the trouble of putting whatever stuff was in there - and maybe after the fact there was guilt, so she added the blanket. That does not mitigate any malice aforethought - putting ducttape on your daughters mouth is prima face intent to cause harm to her. There is your mens rea element, there is your malice aforethought. Show me one jury instruction that says otherwise.