Which is exactly why the whole thing doesn't work. You can kill the sibling or you can kill the neighbor. Tomlinson was the neighbor and they treated him as such. Airiam, despite what anyone thinks, was still just a neighbor, yet they presented the episode as if she was the sibling. The stuff at the beginning was the equivalent to "Hey MC Neighbor, remember how your parents practically raised me and we've always been so close despite never actually mentioning it before and our relationship never extended past borrowing a cup of flour? Yeah. Me neither."