If you’re going to face a dangerous situation, it’s a good idea to bring a frenemy.
With a frenemy, you can work together to make it through a challenge, but if it comes down to it, you can leave her behind as a body sacrifice without too much distress. You care about each other enough to run side by side from something horrible and also concoct a plan to defeat it, but not so much that you’d jump in front of a moving train for her. Plus, if she goes down, you can move on without much turmoil.
Also, you can’t trust a frenemy completely, so you won’t get lazy. You’re not exactly sure if she’ll pack the right things in your apocalypse bag, so you have to pack your own. You don’t know if she’ll snitch to the cops, so you have to act like she did. You can’t trust that she actually killed the vampire, so you need to stake it yourself. I have trust issues, so I think its generally good practice to depend on yourself in clutch situations. But a frenemy by your side forces you to do that.
With a friend, if things really come to a head, you’ll probably feel like you have to save her. Since you’re you, your friend is likely thoughtful and interesting. You probably love your friend and wouldn’t want to survive without her. That’s a recipe for death in a bear attack.
Also, you might rely on her even if she’d be terrible in a disaster. She might be really slow or a bad problem solver or easily scared. Unless you know your friend is a perfect survival partner, tying yourself to her is a risky move. She might get sick because she was too hungry to keep hiking and ate some old fruitcake. And then what? You’d have to hole up in some bunker taking care of the person you love while she pukes to death? Not a good strategy.
And that’s why, when trouble strikes, you better hope you’re with someone who likes the same taco joint as you, but also chews just a little too loudly.