I personally think it means that that person has dies in your mind and heart. I had the similar dream, and ever since I had that dream I think less of my ex and he rests in peace in my heart and mind. I guess it's another way to get over someone you loved sooo much.
Normally death in a dream means an ending or signifies closure, it doesn't actually mean someone will die or that you want death for them. So maybe this means that you are finally over your relationship and that you are ready to fully move on with your life.
It usually means that she will have a long life.
It means you want them to die