You should definitely crate train Maggy and keep her in a crate to sleep, andwhen you cannot supervise the dog and cat! That can be a very dangerous situation, even though the cat is double the dogs size . . you should not tolerate it, especially with a vulnerable little kitten coming. Maggy probably thinks she is top dog, with bed privileges, and being allowed to torment poor Sammy >_< crate training AND obedience training, maybe with some Nothing In Life Is Free training would probably stop this.