Ah, I remember this ol' idea...
I like where you're going with this- and I like the boxes conceit, but I think that it needs a fair bit of work. To me, this is reading like a first draft (no bad thing) but which you definitely need to develop more.
I think FantasySciFi offers some really good advice, but, for what it's worth, here are a few extra thoughts from me:
- Four women alone in the forest, who eventually start killing one another is a decent set-up. The reason why, in my original concept, I had them as Victoria's Secret angels (thanks for keeping the names!) was to heighten the ridiculousness of the scenario. 'Battle Royale with supermodels' is a pretty easy sell, but it also immediately sets the think up as having a satirical core. I wonder whether the set-up might be improved if you made them all lingerie models (best friends still). Opening shot- four lingerie models wake up in the woods. Final shot- one lingerie model stands, covered in blood, amidst the carnage. Ramps up the concept a bit, in my opinion.
- I like the mechanism for finding the weapons; it's cute and effective. I think you need to get to the weapons quicker, and then present some of that antagonistic dialogue once they have the weapons in their hands. The machete to the chest seems a little convenient at the moment- things escalate too quickly, even in such an implausible scenario. Just shifting the order around a little bit will make a significant difference to how that moment works.
- I feel like the ending isn't quite strong enough. It's a fun punchline, but as the folks here have already mentioned, it's requiring quite a lot of exposition to explain. And, to be honest, if we've just watched a brutal four way female fight then we need a strong punchline to match that. I don't have a better idea immediately to hand, but I sort of think that if you can explain the twist visually, rather than through the narration, then the impact will be bigger. I sort of feel like you could have: Miranda finds bloody mary kit – she looks surprised – she looks in one of the boxes – sees note 'A machete, to help you hack through the forest' – looks confused – hears noise and turns round – sees horrified Susanna wearing hen party gear. That's not better, but you get what I mean about it requiring less exposition.
I hope that helps!