Hi, I'd like to help you with your question.
It depends very much on the kind of relationship a person has with their sister. If your sister is very mean and causes you much pain, then you may have a fleeting thoughts about wishing her dead.
However, if someone were close to their sister and was asked about whether or not they wished her dead, the person may become very upset by the question.
As a child, you may say you wish someone dead. Children have little idea of what that means, especially if they are younger. Most children before the age of 10 have little concept or understanding of death. They get the idea but not the details of it. So wishing someone dead to them means the person would still be here.
I hope this has helped you,Kate
Can I help you any further?