The opening scene of Yellowjackets reveals that the show is not playing around with showing just how far some people will go to survive. Cannibalism is a thing in the world of Yellowjackets, and while we still have no idea who the "Antler Queen" or her human-eating subjects are (save for Misty), we do know that they are likely at least some of the girls we've been following post plane crash...and quite possibly the ones we've seen into adulthood. Yet whether Taissa, Shauna, and Natalie actually killed and ate people in order to survive in the wilderness is a huge question mark — and it might not be the real secret they are keeping.
Prior to episode 7's "No Compass," I would have assumed that Taissa, Shauna, and Natalie were still dealing with the guilt over having to physically consume their teammates in order to survive. The show implies that's the case: Taissa's state senate campaign is thwarted by her competitor implying she engaged in cannibalism, and Shauna gleefully kills and eats rabbits, only for it to be revealed later that rabbits are a symbol of her BFF Jackie. Most obviously, we saw young women who we assume are members of the Yellowjackets killing and eating someone, and fellow survivor Misty was in that mix, even if everyone else was masked.
Yet in "No Compass," after Natalie nearly shoots their blackmailer, Taissa makes a comment about not wanting the group to "go away for murder." Natalie replies that they've all done worse than murder — which, umm, is a pretty bold claim. Now, she could be referring to that time they killed and ate their friends, but 1) that would still be murder, and 2) if they just ate people and didn't kill them, that really wouldn't be as bad as murder. So it's either a weird line, or a clue that something else is going on with the trio.
So what might be worse than murder? What if the answer is simple: The survivors abandoned their friends to the woods.
One thing that we don't know about that opening scene — the oh-my-god-they're-doing-cannibalism moment — is exactly when it took place. We know that the surviving Yellowjackets were rescued after 19 months, and that horrible things happened within that timespan. However, what if Taissa, Shauna, and Natalie weren't a part of the worse of it? What if they saw how bad things were getting, and how the woods turned their friends into monsters, and forged their own path to escape? The Yellowjackets survivors would therefore split into two factions: The group that was eventually rescued (Taissa, Shauna, and Natalie, as well as Travis and whoever else is living "off the grid") and the other girls, who turned to cannibalism to survive.
Perhaps the survivors that we've followed in present day were found and saved, but when help finally came, they declared that the rest of the party was dead — meaning, that no one went to look for them, or at least, didn't do so as efficiently as they could to rescue them. Since no one saved the rest of the Yellowjackets, they turned to cannibalism, or just went totally crazy and lost all of their humanity. This might be what Natalie means when she says there's something that they did that was worse than murder: They lied, and left their former friends to become the worst versions of themselves.
That leads us to the Misty question: For this theory to work, how does Misty fit in? Well, we know that Misty is ruthless as an adult, and that behind her cheerful smile is a true psychopath just waiting to be unleashed. (Injecting fentanyl in chocolates?! Crazy!) Maybe Misty played both sides: She stuck by the cannibals in order to save herself, but eventually had to turn on them when she had the opportunity to be rescued. This may be why Natalie is immediately suspicious of Misty, and thinks she's the one sending the postcards: Misty was never one of "them," and only survived by chance — or by manipulation, which seems very her.
With three episodes left, there's still time to unravel all the Yellowjackets secrets...but who is a murderer and who is a cannibal remains to be seen.