I'd just talk to the little child the same way
In fact, I'd make sure to crush her hopes for the future as her gender pretty much limited her role and freedom in society in that kind of era trope
I'd be like "I might not be the hero but you'd be lucking if you could ever amount to my pinky toe. what are you gonna do? Your parents are probably gonna marry you off to some rich old man who also smells like an old man, even before your coming of age. Even if you do not like it, he'll put a child in you and you'll have to spend your whole life with him, hoping he'll die off to some monsters or something. And if he does, the life of a widow is much harsher. At that point, your parents will not be willing to take you back anymore since you will be one extra mouth to feed. Eventually you will have to sell yourself and, after you do so, you will look back at those days with the stinky old man and think they were heaven"
No need to waste treats on the brat. A child's imagination can go a long way and fears feed on imagination. all you gotta do is get that imagination going. Let's turn that child into a doomer, lol