Help with important plot element

Hey, @Silvertide, you gunna chime in here or what? This is your question after all.

You've been given a lot of good ideas, and it'd be nice to know which ones you're leaning to so we can stop repeating ourselves.

 

I once worked with a drummer who had some kind of heart defect (don't remember what so it could very well have been LQTS) and he said he was told he could drop dead at any moment. It didn't stop him from doing strenuous things, though. As I said, he was a drummer (and used two bass drums, no less) and his day job was framing houses (this was pre-nail-guns so lots of 16-ounce hammer swinging). He and his wife were also busy repopulating the Earth. He was fit, healthy-looking and full of life despite his heart defect.

I lost touch with him, so I have no idea how long he lived, but I do know his condition didn't slow him down and he lived life to its fullest. I see no reason why the OP's MC couldn't have something similar.

 

And she could have a banana in her pack.

 

Or she could think her hiking companion is really happy to see her.

Nope. Just a bana-OW shit! Something just bit me!!

 

I'd go with the allergy idea. I'm 26 and have never been stung by a bee or a wasp. True, I've never gone up a mountain, but I don't see why a mountain makes you more likely to be stung? It seems very plausible that she is stung or bitten by something and has an allergic reaction severe enough to kill her, without access to an Epipen. If you're worried about plausibility you could make it a usually non-lethal tarantula or snake that she's allergic to: not as likely she'd have been bitten by one of those before and discovered her allergy.

 

I am sorry for never replying after all this time, I hope I don't get in trouble for dragging a dead thread back to life. I've looked at all your ideas and you don't know how thankful I am. I think I will go with the allergic reaction to the bee or wasp, or the Natasha Richardson thing. Both are good ideas that work perfectly with the story. Thank you everyone for all your input, now I don't have to do something far-stretched like the Australian spider...