Past Promises PP

She was a Queen and he was a King but why he's the only one got reincarnated while she became a ghost?

King: "They say you want the throne and I shall kill you for treason, do you have any reasons for me to spare you?"

Queen: "My dear, you are not only my husband but a King to this nation. I will not resent you, please do whatever you think is the best for this nation."