[ Her tone is more apathetic if anything, but it always has that sweet, cutesy tone to it ]

Yep! I'm going to kill him.

[ She'll let out a giggle as if she just told an innocent joke ]

It's a great idea! It prevents my brother from dying. I mean, the world can live without Veidt. It probably won't make it without Johann.

[ Yep. She's literally implying she'll kill everyone if he dies ]