Well that this point everyone has a reason to kill Ragna for one reason or another, one more isn't going to make him lose any sleep. I think Rachel was just being Rachel, and telling her that if she wants to kill Ragna that's her own business, but when he "dies" she wants Izayoi to kill her too.
But hey, it's just Ragna's luck that he's got apart of the creature that almost destroyed the world attached to his arm, and that it's one day going to revive said beast.