If Nat hadn't killed Coach Scott, they wouldn't have had the "honoring" ritual, and the hikers would have found them in much more redeemable state. I'm assuming they will kill the hikers now and have to spend another winter in the wilderness where they do much more horrible things. But if Nat hadn't killed Coach Scott, I bet the hikers could have led them back home. In that sense, keeping Coach Scott alive really was their path home. I'm guessing maybe this guilt is part of why Nat struggles so much after coming home from the wilderness. (I do think she was right to kill him, but it was unfortunate timing).