That's a horrible thing to happen...
... Cody also shouldn't be financially responsible because other people had an accident at a party he was hosting. It'd be one thing if it was something preventable that he neglected to do as a homeowner. It's not.
I think you can come at this two ways.
To your first point, that Ceci shouldn't be held financially responsible -- in other words ,that it's not fair that he pays the price for this accident. I think I could make a much much stronger argument that the young burn victim shouldn't have had to pay the emotional and physical price that she did. Ceci owned the property -- if it comes down to the question of "fair", his situation is a bargain compared to hers. Regardless of whether his insurance ponies up $8M or not.
To the second point, i.e. the responsibilities of the homeowner. Any "firepit" that requires you to fill it with liquid ethanol sounds like a bad idea to me. Regardless, if I decide to buy one, I can't just then let any old dimwit fill and ignite the thing. Including someone who, when things get intense, just flings a lit bottle of ethanol any which way. I mean, I get it that it went south quickly, but she threw a lit bottle of ethanol at another person. Obviously she didn't do it on purpose, but if you're signing people up for me to share a foxhole with, please eliminate that one from the pool. Yikes.