At the end of the day, the ones suffering are the ones alive. If Kana needed to slap him, let her. This is her way of grieving, and everybody grieves in their own way; there are no right or wrong ways of grieving. Even if this is disrespect, this is her way of moving on, and even Aqua wouldn't be hurt by it. We are no one to judge her, and we shouldn't anyway.
Seems like we are nearing the end of this wonderful manga... And I don't really know how I feel about that, I was here from the release of the first volume... A wild ride
At the end of the day, the ones suffering are the ones alive. If Kana needed to slap him, let her. This is her way of grieving, and everybody grieves in their own way; there are no right or wrong ways of grieving. Even if this is disrespect, this is her way of moving on, and even Aqua wouldn't be hurt by it. We are no one to judge her, and we shouldn't anyway.