Darcy is very young to have such steadfast ideals, but, she could be older than she looks. She might have died as a teenager, but becoming a reanimated entity means she might be much older.

"I apologize, I wasn't questioning your...duty...more your lack of interesting in understanding why. Though perhaps I'm projecting too much." She's willing to admit that. "As for duty, not everyone has to follow theirs. I'm a Hellhound. My instinct is to consume and destroy souls, perhaps a twisted version of my original duty, whatever that might have been."