Laura as a Weapon
I havent seen anyone mention why Laura was such a good weapon. To me, besides the fact that the fireman had a mind in creating her spirit, Laura was a great weapon because of her mother. Judy takes over Sarah because she feasts on Sarah's pain and suffering. In my mind, what would hurt Judy the most is if Sarah suddenly felt tremendous joy. What would bring her this joy? Well how about seeing her daughter alive again. This, for me, is the reason Cooper wanted to take Laura home. It's also why Judy freaked out as Sarah when Cooper was walking Laura through the woods.