I don't think anyone should feel apathy (or joy, not that you do) at the impending death of a human being. Then again, I'm considered weird.

Is this a good friend of yours? If so, would you be able to say to her face that you are not sad over the death of her child? I doubt it (at least I hope not). I understand why you wouldn't grieve for this woman, but it wouldn't hurt to feel sad for your friend. It would break her heart if she thought you believed her daughter's death was justified. It could cause the death of your friendship.