Don't think that Charlie doesn't know.
Don't mistake her optimism for naivety; her occasional lack of tact for a lack of empathy. Charlie's the daughter of a fallen angel and the first fallen sinner; older than most Overlords.
She has experienced enough Exterminations already. Watched slumped sinners, who smiled hopelessly as they stumbled towards the waiting spears of the heaven-sent Exorcists.
Don't think Charlie doesn't notice when Angel Dust wears that same forsaken expression, or that worry doesn't flare up inside her each time she does.
Charlie knows. But she doesn't really know what to do.
(at least, not yet)