I do think Arabella's parents should probably make a point of saying they'll discipline her somehow, but in terms of her specifically, it's in no way our place to punish her. We're just a random who came from nowhere. It was the druids she stole from, her parents are responsible for her. We inserted oursellves into a position we really had no business in. Saying they should make sure she understands what she did is about the extent of it, but our character has no place to demand anything from them. I don't necessarily blame them for not immediately going hardline on her, since they're just relieved to have their daughter back safe. I choose to headcanon that once their relief passes, they discipline her properly. That feels like what would happen in this situation. Also frankly, I think that Rath is reacting a bit over the top to the whole situation when we arrive. Kagha's intent is to just keep Arabella locked away until the end of the ritual, which is realistically a few days to a week away, at which point she'll be given back to her parents. I think that's a perfectly reasonable punishment though I get her parents freaking out. The threat of death by snakebite is a bridge too far but short of that, Kagha's actually pretty reasonable. I just wish she would show more discomfort if Arabella dies.
I fully agree that we should be able to talk to someone about the kids, I suggested it myself. Even if they end up saying "we have bigger things to worry about, I'm sure it's not a big deal." Which is fair considering they arguably do have bigger things to worry about. It's not gonna stop my tiefling warlock from supporting Mol's little venture though. She's got a moral blind spot for her kind.
I have the same exact head canon, so it doesn't really bother me. I expect Arabella will be disciplined in some way outside of my presence. Of course, I get why Rag would like the game to acknowledge as much; it just doesn't bother me in the same way.
Also, I get the feeling that the adults aren't too pleased with Mol. You can hear dialogue from them where the parents respond to Arabella saying, "I don't care what Mol thinks." Or something along those lines. It gives me the impression they believe Mol is a bad influence already.
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As to whether or not it's our place, though...
I'm not sure I agree with you, although I get where you're coming from.
1. If we use persuasion to get Arabella away from Kagha then we end saying something like, "Let her go and *I'LL* make sure she stays out of trouble." --so in this instance, we actually place ourselves in a position where it is somewhat our place to make sure this doesn't happen again. At least, we put our word on the line that we would try to make sure she stays out of trouble.
2. There's also the consideration that children, while being treated differently by the law, are not above the law in societal terms. Now, granted, we haven't been deputized to uphold the law, but it's arguably every citizens' duty to do what they can to minimize violations to the community at large.
As someone else mentioned above, this is a powder keg situation. If I'm in a room with a bomb that's about to go off, I'm not necessarily inclined to leave it alone because it's not my job to disable the bomb. (Assuming I knew how to do such a thing, which of course I don't. Sorry, we'd all blow up, but I would at least try.)