Its a shame that your story isn't a major one compared to project horizons. If it is, and my information on what googling has produced, then congrats. It should be. As there is just enough wrong with horizons to really dislike and worse, considering all that happens, just having to consider some aspects as pandering in part to a certain crowd. (Including some clear copying to mass effect characters.) It is like a SS&E story, enough at the start to get you hooked, then dumps something that just makes you recoil and drop it like a shoggoth gnawing on your hand.
I rather loved kkat's story, I tried it fairly, and with his own views on it, and found it enjoyable. It was a great setting, and I have been looking into more than a few stories, The daily unlife being a big one to enjoy. (The humor in that really sells the story.) Dark shores, another, a soft spot for sea ponies/kelpies. I wish the snakebite story would update again, as the name escapes me for it.
But back to your writing. You nail good believable interactions and emotions that take into account someone that has a whole missing, and run with it well. The past is woven into the present with remarkable means, and does not cross into being remotely near a mary sue, despite the power of many protagonists. What and who they face is balanced well, with thank the stars, smart, clever and strong villains in their field who bar their way. (I couldn't praise you enough for this.) Characters question themselves, and even suffer for who they are, to make a better choice.
Still, i'm rambling, but wish you the best on your writing. And the conclusion here, I know that I will enjoy in proper fashion. What the nasty choice will be for the heroine, I don't, but hope it will be a gut-wrencher.
And this took about three re-writes, as I really had to hold back hammering PH a great day, for it failed to do what you did so well, and with less words needed by far.